What? I Transmigrated into Hinata's Little Sister [Haikyuu!!]

Set in the world of Makoto Shinkai's "Your Name," with the main plot based on Haikyuu!! Blurb: Tachibana Yuta has a secret: every so often, he wakes up in an unfamiliar room, having become a girl named Hinata Natsu. Natsu's habits are completely different from his own. To avoid giving himself away, Yuta learns to tie her hair, play volleyball... and grit his teeth as he tutors her in math. Hinata Natsu doesn't understand why he is always so serious, but she follows his lead, sharing habits, dreams, and the vow they make together: "One day, we'll stand on the national tournament stage." The two tacitly agree never to meet, always assuming their first encounter will be at the glittering national tournament venue. Until Tachibana Yuta transfers to a school in Miyagi Prefecture because of his father's job. He stands anxiously at the gates of Niiyama Girls' High School, but the girl named Hinata Natsu never appears. -- Reader's Note -- 1. Set in the world of "Your Name." The protagonists will switch into each other's bodies. 2. Tachibana Yuta and Hinata Natsu grow up at the same age, but the timelines in their respective worlds differ. Theme: As long as the ball doesn't hit the ground, the game isn't over!