Every Wednesday, there's a man in an animal costume who hands out balloons to kids in the park. The man also hands a balloon to a university student, Yuudai Shimaki, who is on his way to his part time job. Shimaki, while feeling inconvenienced, was unable to refuse. One day, however, he finds the words "I like you" written on a piece of paper attached to the balloon...

(Source: Ichijinsha, translated)