Kyoudai Seido no Aru Yankee Gakuen de, Kyou mo Chigiri wo Semararetemasu

Synopsis

A delinquent boys' school has a sibling system, just like the sister system at a girls' school. Hondou, a delinquent who boasts overwhelming strength, is begged by new student Kurosu one day: "Please be my big brother!" Unknowingly, Hondou finds him cute...?! (Source: Akita Shoten, translated)