Nisekoi

It's hate at first sight... rather, a knee-to-the-head at first sight when Raku Ichijo meets Chitoge Kirisaki! Unfortunately, Raku's gangster father arranges a false love match with their rival's daughter - who just so happens to be Chitoge!
However, Raku's searching for his childhood sweetheart from ten years ago, with a pendant around his neck as a memento, but he can't even remember her name or face!
(Source: ANN)