Going in order of my notes first:
Typo at the content warning (physical vioence)
There's great prose sometimes (particularly liked gravity waiting like a lover), but at the start "he needs your love like oxygen. (...) without you he loses his oxygen tank" is redundant, I don't think the metaphor is so complex you need it explained, so you can make that sentence shorter. "Touches him with ease of ownership" isn't imcomprehensible, but it doesn't sound very good, so I think you can rework that sentence, because I think it can be better, and the character dynamic would be better showcased with a better sentence there (it's a good scene, so you gotta serve the best words to go with it.)
"Don't touch my ear!" sounds a bit unnatural for how someone would talk, and it sounds more like you're telling the audience what he's sensitive about; "don't touch me" doesn't fit the situation, so maybe "don't touch that!" would fit better? This one is a minor thing, but it's a feeling I had there.
Shion goes on to talk about how he's Aksel's savior because he gave him attention when he couldn't bear the solitude of his condition, and while the self-aggrandizing leap itself feels like it came too soon but I won't complain, I think it wasn't set up very well. You should give more time to convey how suffocating it is for Aksel, be it through Shion observing him (telling) or having more scenes with him trying to mingle but being ignored, spoken over, disregarded, etc. (showing). As is, I'm not invested in Shion's obsession, I'm just accepting it because I'm told it's there. But I WANT to feel it, at least.
Aksel and sister are an interesting mystery and what has me the most hooked into future developments at this point.
Regarding the presentation, I think showing what the audience is screaming as images and then putting it again in the dialogue box is redundant, I don't see a need to do that. You could dismiss the dialogue box, or show the images one at a time instead as Shion is narrating to give it a bit of a flow. Where I think your novel will shine more absolutely is with making a custom UI for it. Beautiful art with the default Ren'Py UI is a noose, it actively is bringing down the level of your artistry.
Finally, other than the art being great, the character designs are rich too, every other CG I'm thinking "certainly this is a plot relevant character" because of how much everyone stands out.
P.S: If you haven't read yet, I recommend reading Yukio Mishima's Onnagata.