Ore no Kareshi ga Ichiban Kawaii

Mahiro, a 2nd year high school student, has loved his childhood friend Kaoru ever since they were children. Yet Kaoru enrolled into the most dangerous delinquent high school in their hometown, dubbed "Scum High." Recently he's been dyeing his hair, befriending delinquents, and even getting his ears pierced... Mahiro, feeling uneasy, impulsively confesses his feelings!

(Source: Ichijinsha, translated)