(Ace of Diamond) The Ace's Substitute

Pre-save request: [Diamond A] The Fan Favorite Falls into a Harem Battle in a Sports Anime Born prematurely, Yuuki Aya has a weak constitution. Compared to his older brother and younger brother, who undergo brutal training every day at home, even walking a few steps leaves him exhausted. Even so, he thinks sports are a lot of fun. "Well, if my health is too poor to become an athlete, how about becoming a coach behind the scenes?" He had already decided to fulfill his dream by placing it in someone else's hands. But the people he met changed his mind. "I still want to rely on myself." "Even if, after grueling training, I can only stay active on the court for less than half an hour, I still want to play." "I want to draw everyone's eyes during those thirty minutes." "For those thirty minutes, I'm the ace." P.S. This story has two protagonists. The whole team dotes on Ze. Current timeline: volleyball, then baseball, with basketball woven in between Theme: Saving each other