Boku no Sorciere

Uesaka Kazuhi usually visited his grandfather in the summer with his family when he was small. He once visited the shrine next to his grandfather's house. There, he met a pair of mysterious twins, and since then, he's gone to the shrine multiple times in hopes of meeting them again, but he never did.

Six years later, Kazuhi visited the shrine again for the first time in a while, and there he once again met the twins, who were loitering around just like they did back then.

The two seemed to not have changed at all, as Haruka still had her beaming smile and Ryou was just as mature. but...!