Ppoi: Hitonatsu no Keiken

The protagonist Sawahara Asumi is a 3rd year middle school student who is part of the basketball club at her school. Taking a break from studying for her entrance exams she goes to hang out with her older sister at her apartment for summer vacation. But she accidentally runs into an unknown girl and they switch bags, in a panic Asumi runs after her and ends up lost.

She ends up running into Taira and his friends and they end up finding her bag, but then Asumi notices that her precious wristband...