Nisekoi

When Raku Ichijou was young, he made a heartfelt promise to his childhood friend that if they were to meet again, they would marry each other. Ten years have passed since that fateful day, leaving Raku's memory of her faded. But he still holds a relic of their relationship together—a locked pendant, which his childhood friend holds the key to. He hopes to reunite with her one day, despite not remembering what she looks like.