Punch!

Elle Nagahara is a 1st year in High School. Her grandfather and his rival, later friend made a promise, that their kids would get married. But they both had sons, so now the promise falls for the grandkids, Elle and Ruo. Ruo wants to marry Elle, but Elle want's a normal life. Everytime she falls for a guy, her grandfather sends few students from his gym to scare the guy off. It worked on every guy, untill Kazuki Shindo. (Source: ANN)