I Can't Become an Adult.

Satoaki, who harbors feelings for his childhood friend Rikka, is afflicted with a mysterious illness that stunts his growth at a young age. He belittles himself, feeling he can't become anything, and continues to think of Rikka even now that they've grown distant. One day, on his way home, Satoaki unexpectedly reunites with Rikka…!?