The Gravity User Refuses to Become a Babysitter

To save his companions from the past, Chuuya is invited by the System to return to the past and change their fates. Only... Chuuya: "Huh? You want me to win Verlaine over with love? Are you kidding? Can't I just use my fists?" As a ruthless Mafia member, Chuuya refuses to become a babysitter to a bunch of kids, but he can't stop the System from insisting: "Host! When Verlaine first appeared, his body was thirteen years old. He's not a child anymore! This white-haired, blue-eyed kid is a child of God, so he shouldn't count as a child! This bespectacled kid has a high schooler on the inside, so he's definitely not a child! What? Host, you think they're too rowdy? They don't act like adults at all? ...That's fine. Look at this one, a super-cute little bunny. This one's a real child!" Chuuya, buried under a pile of kids: "..." (gradually growing irritable) After struggling to survive in unfamiliar France with a whole family in tow, he finally completed the mission. But when he opened his eyes again, Chuuya discovered he had returned to age fifteen, and their worlds had somehow merged! On his left was a white-haired high schooler, grinning and joking, a whole head taller than him, who exclaimed in amazement, "Wow, from this angle, Chuuya's so tiny!" On his right was an elementary school detective, on the verge of tears and muttering, "Chuuya, believe me! I really don't have a death god aura. The old geezers Gojo talks about died purely by coincidence!" In front of him was a brown-haired middle schooler shouting, "Chuuya, help me!" only to get hit by a baby, then lie on the ground bawling with a huge lump on his head. Not far away stood a golden-haired god, looking conflicted as he wondered, "Should I call Chuuya big brother or little brother?" Chuuya: Thunderstruck.jpg Reader's Guide: 1. The System is just a plot device. Apart from the early part where it needs to explain things, it won't have any other role. 2. An original French Transcendent will appear in the story. 3. No side couples apart from the brother and sister-in-law. 4. Chuuya won't return to the Port Mafia, but changing his mind will take time. 5. More to be added if anything comes to mind. Theme: Stay optimistic and cheerful.