Sankaku Twilight

Miki, a delinquent who enjoys fights and is feared by those around him, ends up becoming a library committee member with Ikkei, who is his complete opposite. While they clash due to their contrasting personalities, Ikkei learns one day that Miki has a crush on his childhood friend and senior, "Watarun." Despite the surprise, Ikkei supports Miki without prejudice and somehow becomes cherished. Initially, Ikkei couldn't stand Miki, but as time goes on, he starts to find him adorable...?

(Source: Tokyo Mangasha, translated)