The Pain in My Heart(2006)

Boku no Mune ga Itakutemo: Glass

When Kousei Matsumoto finds a a man apparently suffering from heatstroke alone out on the street, he takes him despite his better judgement. The young man is a mystery with a scar he won't explain, and the only clue to his past is the whispered name "Mori." Despite this, Kousei finds his heart becoming entangled, and the pair forge a fragile relationship. When the past literally comes knocking at his door and the truth of the young man's true identity comes out, Kousei comes to a decision that literally tears the pair apart. But is it the right choice, and can the lonely, waif-like stray face his past and forge a future that includes Kousei?

(Source: DMG)