Hikatte! Tsukishiro-san

Tsukishiro is a bus driver living with a peculiar secret: his hair emits a soft glow whenever he experiences feelings of joy or hope. To hide this strange condition from the world, he leads a solitary life, ritually casting away any positive emotion he feels from a bridge. Unable to open his heart to anyone, he is utterly alone. One day, pushed to the edge by despair, he decides to end it all. But just as he's about to take the plunge, an encounter he never could have foreseen will set his life on an entirely new path!

(Source: Shogakukan, translated)