The Supporting Character Just Wants to Survive

"Kid, you've hit the jackpot!"

Bang!

"No!"

Due to circumstances beyond anyone's control, the boy is reborn in another world. What's more, it's a magical world based on a harem novel he read in his previous life, and he is a nameless supporting character. Thinking of all the trouble that will befall the "protagonist" in the future, the little side character shudders. So, in order to stay alive, he begins his school life, determined to remove every little death flag.