https://www.mangago.me/read-manga/cure_blood/
ill find more later
https://www.mangago.me/read-manga/haruka_tooki_ie/
https://www.mangago.me/read-manga/happy_of_the_end/ - happy end soz, but i really really like this.
this one's nice too, but its the ml who's suicidal
https://www.mangago.me/read-manga/on_the_lake_where_the_waves_reach/

Any suicidal MC in modern setting?
No romance (exemption of a tragic one)