SoniAni: Super Sonico the Animation: Temporada 1, Episodio 4

Sonico gets a postcard from someone with no sender written. It seems to be from a tropical location, and there's only a few words printed. Sonico remembers her past. Everything started when she was into rock during middle school. She couldn't express herself honestly and with as much power as a rock musician, so she wanted to be like one. She finds a upperclassman who teaches her everything....

そにアニ -SUPER SONICO THE ANIMATION-