Mamotte Banken-kun

Masa, once a crybaby who faced bullying in his childhood, resolves to become stronger after being dumped by his first love. Now feared as “Masa the mad dog,” he spends his days battling delinquents. Everything changes when Morizane-kun transfers from a prestigious all-boys school. With a striking resemblance to Masa’s first love, Morizane also appears to know more about Masa than he lets on...?

(Source: France Shoin, translated)

Note: Chapter count includes 2 extras.