MTL - Immortal Becomes a Stay-at-home Dad After Return - ~ 537 Auntie, you are stealing the concept!

A high school student that has lived as a mob-character ―― Mimori Touka

ln the Higher Realm.{Ehhh! It’s started?} an entity exclaimed.{Yeah, but like, what the hell—she gave the golden finger to him? Of all people, someone useless and a scheming bastard?} another shot back, clearly not having it.{Someone Immediately Stop him he's corrupting the system!} An entity roared before they could even get ready for see how had had been chosen!___On Earth.[System Integration... 1%A wicked grin spread across his face. This was his chance—a chance to do something no one in those web novels and mangas and animes had ever done. To corrupt the system!minute later....[System integration... 85%...][System integration... 99%...][Integration complete!] It ran one last time...“Did I succeed?”And so the journey started.

Yuki, a high school junior, dies heroically saving a stranger and is reincarnated in a fantasy world, where he discovers an extraordinary and unrivaled power.

Noda Sagiri is the only girl in her karate club, she has little feminine attributes but has a hidden talent in making sweets. On a whim she decided to bring her handmade cookies to her club, but after one of the idols of the school Michel François tasted her cookie he suddenly declared “I must meet with the girl who made these cookies!”. The search for the cookie maker began, however it seems that no one would come to expect that Sagiri is the one who made them….