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I want to eat your pancreas (girl has an illness. Frequently in the hospital)
Your lie in April (girl has an illness)
Devil's line (no illness but the guy is a vampire and cuz of that he seems to be too cautious)
http://www.mangago.zone/read-manga/haru_no_noroi/ (girl is suicidal)
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But i also have a rec here. Took me some time coz i forgot the title so need to look it up againXD.
"the friendly winter" - A girl with a rare growth disorder that leaves her in the body of a child at the age of 19 meets a boy with a mental disorder who has the mind of a small boy in a 17 year old form. A Friendly Winter shares with us the endearing story of their day-to-day lives, joys and tribulations.
Something where the main character has some sort of mental illness or disorder. Thx