Despite the tragic nature of this Manga I think a lot of (japanese) storyteller could learn from it for one thing, CARROT AND STICK, is not a constant slide downward toward misery.
Also, they are more comfortable together than a lot of couples are in Manga (looking at you Dress up Darling).
Take that lighter but still dramatic Manga of the guy who leaves the abusive GF, despite the drama being nothing like this one, it has just been stick and stick, no victory, no nice moments for our MC (unless it happened in the last chapter or so).