I dug up an idea from my collection of story concepts, one I'd completely forgotten about. I'll put the premise here first. I quite like it.
Jinguji Ren, male, 16. His hobbies are tennis and... cosplay.
On the court, he cosplays other tennis players to create his signature move, the Niou Illusion. Off the court, he's just as devoted to cosplay, dressing up as all kinds of anime characters and making his own costumes and props.
After the U17 World Cup ended, Niou resolved to seal away his Niou Illusion on the court and explore a new path in tennis. Then, off the court, he suddenly discovered that every day he gained the abilities of an anime character he'd cosplayed in the past.
Niou: Why bother sealing away the Niou Illusion? I'm not doing that. Cosplay is so much fun!
Maybe the inspiration came from... Martin Morning?
Blurb posted February 15, 2022.
Theme: Every day brings a new Niou.
