As you take your time, and think things through, it becomes apparent that you don't need to make an escape attempt to be able to exit and remain outside of Shina for a relatively short period: you could just ask for her permission to do so.
At this point, you know she is gentle enough to care about your desires, and thus, if you can convince her that this is going to be a temporary thing before you return to her as soon as you're done, she's likely to accept. Besides, it would allow you to potentially explore her whole home, which could be interesting as well.
Thus, you quickly devise a plan: on the night of the following day, after she had fun with you at home before dinner, you then would try speaking with her, telling her that you would like to explore her home and remain outside of her for a short while before returning.
You are confident that is going to succeed, but it is not assured: if she refuses, you have plan B of trying an escape attempt.
So, the day passes, and the routine remains usual: still in the mornings while the girl is at school, games during the afternoon at the cafe, and immediately after she comes home.
It was when you had succeeded in making Shina climax by licking and caressing her G-spot that the plan was set in motion.
"Mmm...That felt as good as always, my dear pet...come here, you know the drill, hehe." the giantess said while bringing her hand close to grab your still form.
As she brought you through the air, ready to insert you back into her nipple, you cried out:
"Shina, wait!"
You tend to remain silent on most occasions, so hearing you speak outside of the conversations you usually have before going to sleep was unexpected; in a surprised tone, she replied, asking:
"What it is, dear pet? Is something wrong, did you got hurt when landing from my boob this time?"
"No, it's not that: you see, these past days I have wondered if I could explore your home, to get to know more things about my owner and her world. Also, there are chances that I might find interesting things that could take me some time to unpack while doing so, so being able to remain outside of you for a short while would be appreciated."
The giantess looked at you curiously, for this is a weird request: sure, she expected that you could one day ask her to explore her home but being allowed to stay outside of her for some time? She was... hesitant about allowing that.
In a tone matching her now worried face, she said:
"I...don't know, my dear pet: it is one thing to ask me to let you explore, for I could easily keep an eye on you for the duration of it but...letting you remain outside of me? My home might be small, but I am certain that from your perspective it would be still enormous, full of dark places and corners: Who knows what critters might be scurrying around beyond my reach, small to me but dangerous to you! I don't want to risk you getting hurt."
She speaks true, for your size makes you vulnerable to any potential thing that is small enough to move beneath the furniture of her place, hidden from both sight and reach and thus being a threat should you find yourself beyond Shina's notice. It is no wonder why with that in mind, she has always kept you within her, absolutely safe from anything.
However, she is not denying the possibility outright, which is a good sign: argue some proper points, and you will be able to convince her. You speak, saying:
"I know, that's also why I have been hesitant on my part to ask you something like this: I trust you will keep me safe when you're awake, and I promise to both be careful when you are asleep and to return as soon as I'm done. So, please, could you let me?"
You then grasped your hands together, and looked at her with the cutest, pleading face you could muster: you didn't want to be forced to escape her to go chatting with the ghost, driving you to give your utmost to obtain the giantess's permission.
Shina looks at you, before sighing. She then smiles calmly again, speaking while doing so:
"Ok, ok, I can't say no when you put on such a cute face! Very well, you can go exploring my home in its entirety, but not right now: I want to introduce you to my roommate first, so that way we together can keep an eye on you for as long as possible."
"Thanks, Shina, I appreciate it! I can't wait to return with my dear owner once I'm done!" you reply, cheerful as you grab the closest finger, your closest attempt to a hug you can provide.
The girl just giggles, finding your reaction wholesome. She then brings you back inside, where you immediately curl up, deciding to take as much of a nap within her as possible, for you will not be able to enjoy its warmth for some time.
The next day went as usual until Shina arrived home: this was one of the days of the week when she could count on having her roommate at home, instead of her still studying until late at her college, for she was a couple of years older than your owner.
"Hey, Kat, how are you doing? Are you free? I want to show you something." you hear your owner's voice.
"Sure, girl, I can rest of studying for a while. What do you want to show me?" replies the other girl.
"Well...we have had good times, so I trust you with a secret: I have a tiny, and I would want to introduce him to you," says Shina, a hint of nervousness in her voice.
You hear a gasp from the other girl, before you hear her speaking again, saying:
"A tiny? Hehe, no wonder why these days you have always gone straight up to your room, locking it with key and everything; you also take each time a good amount of toilet paper with you. Let me guess, you were having fun with it before dinner?"
"Yeah...that's has been why: he's rather good, always making me..." says Shina, before suddenly stopping.
Trapped inside Shina's breast, you immediately wonder why the sudden silence, but thankfully, this "Kat" helps you unintentionally when she speaks, in a teasing tone:
"Hehe, no need to be shy, Shina: it's always good to have a tiny one who can make you cum with their little struggles and efforts. In fact, why don't you show me where you keep him? I am curious as to where you prefer to have it."
"I don't know, I have never..." says Shina, clearly hesitant to directly show her roommate where she likes to have you.
"If you have issues, I can strip down myself to make you more comfortable." says the other girl; she is bolder than you could have imagined, lacking any hesitation whatsoever regarding showing off to another individual her own naked body.
"No, no, that wouldn't be needed, at least not fully: just showing off your chest will suffice..." says Shina. You hear a level of embarrassment in her voice, yet she seems more eager than before.
"Fair enough: it is because that's where you keep your tiny?" asks the other girl.
Shina doesn't respond with words but likely asserts in the affirmative, as you can see and hear how she begins to strip down her upper clothing, while you can hear similar noises occurring some distance away.
Then, you feel how the giantess begins to push you outwards until your own upper body peaks out from her nipple. You're then gently grabbed between two fingers that leave you on top of an open palm.
When you adjust to the new levels of light, you look around, and soon find yourself looking at another giantess: she's slightly taller than Shina, with Short brown hair with matching eyes. Her facial features are slightly more mature than Shina's, yet not by a long shot. Her chest on the other hand, although well developed, is "small" compared to what your girl brings to the table; you knew they were BIG, but until now lacked any point of clear reference to prove it with certainty.
"Tiny, this girl is Katarina, or Kat for short: she's my roommate. Kat, this is my tiny," says Shina, introducing you to the other inhabitant of this place.
Kat slightly bends, to get a closer look at you. She stares at you for a few seconds, before she smiles. As she returns to her straight posture, she speaks to Shina, saying:
"You're a lucky girl: your tiny is rather good-looking, like having a tiny cute boy in the palm of your hand; I have heard that most tinies tend to have rougher features, with some being compared to ugly old men: no wonder why you refer to him similar to a person instead of a thing."
"Well, I had no idea about that, but I promise: I would have taken good care of any tiny, no matter their appearance," says Shina, in a bid to show she wasn't acting biased towards you because of your physique.
Kat just looks at her roommate with a raised eyebrow: she's not convinced that would have been the case. Yet her face turns to a more neutral stance, as she asks:
"Well, this is fine to learn, yet I doubt that you chose to show me this just because you felt like it; we are good acquaintances, but I never thought we were close enough for this."
"True, that's correct: I would have shown you my tiny perhaps later, once we were closer, yet circumstances required me to make this now. You see, my tiny wants to explore our home, and I would appreciate having your help keeping an eye on him while he does so."
The other girl raises both eyebrows, shocked as to why her roommate had done this. In a tone matching her face, she asks:
"Wait, did you do this because your tiny asked you? Damm, I had heard about girls being kind to their special property, but not to this level: however, I am less shocked thanks to our previous conversations, you always seem like the kind of girl to go the step further for anything they care about."
"What can I say? I care for my pet, and thus, allowing some wishes and desires for him will only serve for us both to have a blast of our time together. Isn't that right, my sweet pet?" replies Shina, while bringing a finger to pat your head.
You nod in agreement, and Kat finds the whole interaction between you two wholesome. She comments no further regarding how Shina treats you: sure, this was truly unorthodox behavior, but she never had a big opinion regarding how tinies are meant to be treated.
Once this chat was over, your giantess crouched, allowing you to hop down from her hands and onto the floor. As you looked high, you saw how the two colossus were looking down at you. It would have been a rather shill-inducing experience, if not for the fact that they were looking at you with warm eyes. Shina speaks, saying:
"Now, go around, I am sure there is plenty to find at your size. Be careful, and remain within sight wherever possible. If any nasty thing finds you, just right into the open and cry out loudly, and I promise to be there to save you."
Kat meanwhile nods in agreement, before she confirms you can count on her as well.
What follows is a rather interesting journey for you, for your only experience traveling on the floor of a building since you were shrunk was those ruins where you learned spells. Compared to them, this entire apartment was way smaller but in far better condition, with all the rooms and their furniture in pristine condition.
These two girls are diligent when it comes to the maintenance of their home, for you find little dust and dirt wherever you go: only on the most hard-to-reach corners and spots is any proper amount of them, and even then there is little to provide shelter to any bug that might scurry around. Therefore, these girls make it a lot safer your travel, not finding any bugs at all.
While you travel across the rooms, you can feel from time to time the gaze of one or both of the giantesses, who currently are chatting while they eat dinner together at the main table; you turn around and wave at them as signals that you're ok, acts that make Shina visible giggle; she appreciates that her pet keeps his part of the bargain, constantly walking where he is fully visible wherever possible.
This goes down for the rest of the evening until you're certain that there is not a single uncharted corner of the apartment. And, as you expected, the ghost is nowhere to be found, not at this time of the day. You approach your owner, trying to get her attention. Once you do, you say:
"Hey, Shina, I found something, a weird piece of scrap metal: I promise to return it to you as soon as I can shape it into something presentable, as my gift for how you have taken care of me."
"Aww, thanks, little guy! I can't wait to see what my little pet can offer to me. Again, just be careful!" says Shina, squatting a bit to be able to reach to pat your head.
Meanwhile, Kat just looks, bemused as to the degree of autonomy Shina is willing to provide her pet.
Soon enough, Shina stands up and goes to bed. Her roommate followed soon shortly after.
Darkness begins to rise, and you go to a special spot you found underneath the couch in the TV room: there, with some small wooden fragments and wool treads you built before what you could call a small bed, where you lay to rest until later.
It is hard, and not because of the material: a part of you finds it hard to accept the need to lie to Shina, even though it was a lot more believable than the "hey, I need to talk to a ghost" deal.
Yet, you accepted it eventually, allowing yourself to rest until the right time.
Waking up in the middle of the night, the distant snoring sounds you can hear tell you that you awoke at the right time. Determined, you exit your current quarters, and head straight to Shina's room.
There, you look around, and by the dresser beside the bed, you can see a lightly blue figure.
Its semi-transparent nature becomes clear to you once you get close enough: however, it remains with a clear shape that is of a tiny young man, similar to you. When you are near, he looks straight into your eyes and says:
"Ah, so the little light has found me at last. You took...longer than I expected."
Before you can reply, he continues speaking, saying:
"But that doesn't matter; you're here now, and I can finally see you with my own eyes. After all, it is my duty I ensure you're a worthy new pet to my beloved Shina."
At the mention of the term pet, you can't help but scowl a little: deep down, you are still reluctant to fully accept such a moniker, even if an accurate description of your current status.
Well, the ghost does notice your reaction, frowning hard as he begins to speak in a harsh tone and saying:
"What is that look for? Don't tell me you still don't accept your role as Shina's pet! What better owner could you ask for? Just think about what she does for you every day, keeping you safe! You'd end up the same as me much faster without a loving owner like her!"
"Hey, I know, I know...sorry." you blurt out, attempting to calm down the angry spirit.
After a sigh, you continue, saying:
"You're right: Shina does keep me safe, takes good care of me but...I don't know, I wish that she...treated me closer to the individual that I am, allowing us to be...something closer than only persons can have with each other. Sorry if I sound selfish for such a desire."
After hearing you explain yourself, the ghost does calm down, saying:
"I understand, I too once wished I could be something more intimate with her: she is kind, caring, and cute. What is there not to fall in love with? Yet we can never interact in such a way: the earlier you accept that, the better."
He sighs for a second before continuing speaking, saying:
"Now, my apologies, but after this whole rant I have realized I have yet to introduce myself! Hello, my name is Fluffy; as you likely are now aware, I was Shina's first pet: I guess that her guilt about what happened must be eating her stronger than I could have imagined, with you learning this from me instead of her; yet knowing her as well as I did, she would most likely not want to frighten her new pet with such a terrible story regardless of that."
As he now turns sideways, his gaze laid upon the gorgeous naked colossus sleeping soundly in its bed, sorrow fills your predecessor's voice while he returns to speaking after a heavy sigh:
"I just wish I could make her smile one last time...she used to have the sweetest laugh when I would wear my uniform..."
His eyes then go wide, for a realization on his part has been made. He then turns his focus back to you, and in an energetic tone, says:
"Wait, there is a way, something that might work! Listen, up on top of this dresser there is her jewelry box: she probably kept my uniform in there; just climb up and put it on. I hope by you doing that, she will remember the good times she and I had together instead of the final terrible event."
You look up the gigantic furniture, and then back to the ghost with hesitation plain in your face: it is quite the climb, and there would be little to nothing keeping you safe from damage should you lose your grip. Fluffy immediately notices this, leading him to speak again, saying:
"I know, it is a rather heavy and potentially dangerous endeavor, but I promise that if you do this, I will give you my blessing and explain everything: believe when I say this, a blessing from a ghost is no small thing for us tinies. However, I can understand that you might not be eager to try, at least for now. I can wait here until you're ready to climb."
Thus, your path forward lays open to you: in return for you risking your skin to get to the top of what is to you a large cliff-like furniture, Fluffy promises to not only provide the full details as to what happened but also his blessing. By the looks of it, he is perhaps aware that you have magic at your disposal, and by helping him you could obtain either a new spell or strengthen one you have at hand. Not only that, if all goes as planned, Shina might find the whole endeavor rather cheerful to her.
However, it entails risks, and perhaps you are not willing to try it, either in the short future or...even forever.
In the end, it all comes up to what you consider most valuable: Shina's spiritual well-being and further progress with your abilities, or your current safety and comfort.