Hen Koi! (ヘンコイ!) is a manga series by Tesshin Azuma. It was serialized in Young Champion Restu from October 16, 2007 to October 20, 2009.
Watase-kun is an ordinary high school boy, nothing special about him, unless you count that someone is secretly vandalizing his possessions after school each day. With very little clues and even less of an idea, he sets out to catch the perpetrator. However, he discovers that once again another of his school items have come up missing. Feeling that enough was enough, he attempts to catch the violator in the act red handed. What he finds very well may change how he see his little world.