Hasegawa Kouta is a completely average second-year high school student. He feels as though something is missing in his life and that it's impossible for someone like him to have a shining school life. Then one day, as he's out with his friends, Kouta encounters a missing little girl and she gives him a Pompompurin sticker for helping her find her mom. This reminds Kouta about how he used to love Pompompurin as a kid, especially because of the giant stuffed Pompompurin his beloved grandmother gave him as a birthday present, but was forced to cast that aside due to peer pressure. However, at school he picks up a lost My Melody keychain and realizes it might belong the very flashy and popular Mizuno Ryu, how is this possible?

Kouta's classmates, Mizuno Yuu and Yoshino Shunsuke, reveal that they too love Sanrio characters and are self-professed, "Sanrio Boys". And, much to Kouta's surprise, they feel no shame in admitting that they like these things! Kouta has a hard time accepting this and tries to avoid a very intense Yuu bent on becoming his friend, but finds himself unable to avoid his new acquaintances. Meanwhile, when Kouta's stuffed Pompompurin, a beloved token from his deceased grandmother, winds up accidentally being sent off to the recycler he takes off in a desperate search to try and find it. At his wit's end Kouta is happened upon by Yuu and Shunsuke and wonders why they can admit was he has never been able to.