Tsujiura-san to Chupacabra

Tsujiura-san to Chupacabra (辻浦さんとチュパカブラ, lit. "Unidentified Mysterious Girl") is a manga series by Atsuhito Sakurai. It was serialized in Shonen Champion.

Plot
An ordinary, bored, bullied high-school boy. A mysterious, frail and cute transfer student who just happens to be a feared delinquent and studies the Chupacabra. They meet and start going out together. What can go wrong?