Wow.  This was...actually, it's hard to find any words to apply to it.  "A lot" seems an insufficient phrase, but also sums it up best.  ;)  I appreciated how the story balanced the heaviest moments out with lighter moments to let the reader catch their breath, as it were.  (Though I still had to stop and do something else for a while after the scene focusing on Nina.  It's been years since I lost my kitties, but I still feel that pain all too strongly.)  I can see why you didn't want to put content warnings on this; the length of the warnings would have been horribly off-putting, and also spoiled most (or all) of the turns in the narrative/conversation. 

As a fellow dev (dev-in-training? dev-wanna-be?), I was also especially struck by all the visual effects--the blurring, darkening, lightening, etc.--and I will absolutely be looking for a tutorial to be able to add those to my own works.  :)