Kimi to Parade / Paradise view ?
Mo Dao zu shi, you litteraly just described it
Its a beautiful love story, not focused on the fact that they're gay, they couple be a lesbian couple, trans couple... whatever, it focuses on the love between 2 boys, a love full of pureness, both becoming soulmates for life. The hardships that they went through... where every single person was against their love one and even so they stood by their side.
Let Dai
Tatoeba Konna Koi no Hanashi
Yukidoke no Koi / Bokura ga Koi wo Ushinau Riyuu
try them (maybe sometime they are not truly tragedy but they translate so well reality (in my opinion))
July Found By Chance
To Take an Enemy's Heart
Chew and Swallow
Jazz for Two
a story line which is a beautiful tragedy like when they overcome hardships and have a difficult time but it still works out in the end? can't give an example because I haven't found one yet. idc if it's yaoi or shounen ai or if it's friends to lovers, vampires, popular x loner etc.