Watashi Yori Tsuyoi Otoko to Kekkon Shitai no Seiso Bijin Seito Kaichou (Jitsuha Moto Banchou) no Himitsu wo shiru Kage Kya (Jitsu wa Kanojo wo Koeru Saikyou no Yankee)

Akira Kogure, a boy who was a bit of a nerd, accidentally discovered that the beautiful student council president, Shizuka Takasaki, used to be a delinquent girl-gang leader. She said she would only marry a man who was stronger than her. But it turned out that Akira was actually also a former delinquent even stronger than her. (Source: Fantasia Bunko, translated)