this manga's genre is definitely an eroguro and maybe the author is a fan of that genre the story is quite uncomfortable bc its full of misogyny, also their romance is all about violence. i really think that makoto (the guy) was a realistic yandere and not a romanticized one, like if yanderes are in real life? they'd be like makoto (and yep, they're fucking scary)
i think he just liked the idea of "destroying" mikoto's (the girl) innocence and somehow putting another person into his shoes (as a victim of abuse).
the ending was rather nuanced imo? maybe makoto's started having genuine feelings for mikoto and seeing her getting into it (being murdered) was something he doesn't want to happen (the hospital scene where she confessed to her desires). rather than dying at his hands, he couldn't do so now he doesn't want mikoto's life to end. (beach scene where makoto covered mikoto's eyes to prevent her from imagining that she's dying/dead by drowning)
i also think that makoto projected his past self (he was groomed and abused by his "brother") to mikoto, and seeing her accepting him slowly wasn't something he plan to do. i think makoto really wanted to be hated and that mikoto reject her (as much as he want to do so to his brother). and after seeing what mikoto had become (adapting to the abuse etc) made him repulsive as he saw himself too.
anw its too long alr but it was trash. poor translations, weird story pacing (there were chapters where its all about their daily life then switches to a dark psychological scene), character backstory wasn't explored that much (implied only) so there's no character depth, there's so many unsettled story points (ex: on shuichi's and his brother's path, the new girl of mutsumi, saki's path) which had potential if also explored.
the story got me hooked, FL's trait and situation was unique and as i continued reading it gave off the vibe that it became an "utsuge"