This is the manga that finally made me get an account in order to comment, mainly because the ones I have been reading are so far away from my own interpretation.
The ending didn't strike me as happy, but more as a ruthlessly desperate compromise. And as in all good compromises, nobody is truly happy. Trying to reconcile his broken dreams and ideals, his once pure feelings with the repeated trauma of being raped and taken advantage of, unable to relinquish the good parts of what he experienced, yet also struggling with guilt and self-blame.
Maybe I am reading way too much into this manga, but it is truly a beautifully written and drawn work of literature. I am certain I could return again in 1 year and in 5 years and experience this story entirely differently, because the way these heavy emotions and actions are displayed leave that space for interpretation.
Sankaku Opera