Class Teacher System - Chapter 1: Save the psychopathic killer ()

There are Humans. There are Elves. There are Dwarves. There are Orcs. And then there are Demons, and the Demon King.In a world where warriors wield elemental fury, assassins bend shadows, and mages rewrite the laws of reality with a thought… one boy awakens the weakest and funniest ability of all.[Muscle Genesis]… the power to grow and control muscle.The f*ck? No sword aura, no magic affinity, no flashy technique, just raw, brutal power.Born in the wild slums of Arcanum Nexus, orphaned, starving, and forgotten by the system, Kairo Vale has one goal: survive long enough to rise above it all.When his chance finally comes in the form of the prestigious Nexus Academy Entrance Tournament, the world expects him to fail, just another Unranked slum bastard with a useless ability.But the thing about muscles is that… they grow.And so does his pain tolerance, and his strength, and his will to endure.Thrown into trials designed to break him, teamed with nobles who want him gone, and hunted by powers that fear what he might become, Kairo fights back the only way he knows how: one rep, one punch, one brutal threshold at a time.Because in this world, power is everything.And he’s going to build his from the ground up.If they won’t give him a place in their world, he’ll carve one with his fists.

Xia Zhijun got the title ‘study god’ after scoring first place in the whole city. He’s the model of a good student in a teacher’s eyes: good grades, good manners, and quiet. When he wasn’t smiling, his entire body emits a cold abstinence aura. The girls only have the guts to look from afar and not get close.
Later, it was rumored throughout the entire school that even the study god would fight and hit on girls. Whoever dared to provoke his girl, he would teach you how to be a person at every minute. The night of the graduation ceremony someone saw him blocking Gu Siyi in the corner. He didn’t stop kissing even when she cried. He bit her lips and said in a raspy voice, “I’m going crazy…”
During college finals, Gu Siyi almost bursted out crying, “I’m such a failure. I won’t be able to find a good job in the future…And if I can’t find a good job, I can’t provide for myself…”
Xia Zhijun played with her pink earlobe and remarked, “I’ll take care of you.”
After they graduated, Xia Zhijun created a research company and Gu Siyi became the boss’s wife.
The commercial rocket, “Star of Siyi” was successfully launched. So everyone knew that the new technology superstar, Xia Zhijun has a wife who he spoils a lot.

- Description from Novelupdates

After 140 years that gates and dungeons appeared on Earth and a system allowed humans to use special abilities, Matthew an 18 years old who just got out of high school will seek adventure inside those perilous places. However, instead of being able to select his own class as he progress the levels, destiny has another plan for him.

Rowan Mercer was never meant to exist. Born in a covert mutant lab as Subject 757, he was engineered from the genes of Professor X and Magneto, then dismissed as a failure before he ever learned what he was capable of. His telepathy is faint, his magnetism weak, and the scientists who built him see him as little more than a disposable prototype.But Rowan is not alone in his own skin.The night he tries to sleep off another brutal training session, something in him fractures. His consciousness splits open, anchoring him to a second body in a different world entirely—an abused orphan in the shadows of Knockturn Alley, just days away from entering the wizarding world.Two bodies. Two lives. One mind.And then Rowan discovers the real impossibility:Every ability he trains in one world strengthens him in the other.Magic fuels mutation. Mutation fuels magic. And each new universe waiting beyond these two is another life ready to awaken.With X-23 preparing to lead a desperate escape, the wizarding world whispering of ancient power, and the multiverse itself unfolding like a map only he can read, Rowan begins to understand the truth:He isn’t a failed experiment.He is the blueprint for something the multiverse has never seen.A survivor.A weapon.A convergence.And the worlds that created him have no idea what he’s about to become.