Angel's 3Piece!.

A shut-in ever since he had a traumatic experience, Nukui Hibiki's biggest hobby has been using vocalization software to create and uploading songs online. One day, he receives an email from some fifth-grader girls, asking to meet and discuss something with him. The three girls, who have grown up together almost like siblings, ask him to help them show their gratitude to the people who have taken care of them. The method they've devised? Putting on a successful concert at a place full of memories.