Rin used to be your boyfriend, but now he has someone else, so you should learn to let him go. but, what about the promise? he promised never to leave you, and he promised to beat up anyone who tried to hurt you. and now, he broke his promise, he's chosen another woman to be his life partner. you two also had a beautiful dream together, which was to get married and have a happy little family, but unfortunately, that dream can never be achieved now.