I Gave Up Being Stronger - Chapter 408

Xia Yan passed through to the world of Bleach and became an eleven-year-old boy. He was rescued by Renji and Rukia in the Seireitei, and he was studying at Shin’ō Academy, and he was a student of the same class.
He is a top student of the Shin’ō Academy, and he is vying for strength by various teams. In the end, he has entered the first team of secret mobile maneuvers.
He will use punishment to kill every person who tries to threaten the martyrdom and protect his loved one.

- Description from Novelupdates

800 years ago, 3000 dimensional gates opened across the entire world. In that moment, it was as if 3000 different colored eyes opened across the world as hordes of monsters swarmed out of these gates like tears.

Some could destroy city walls with one strike; They had bodies the size of a giant and fed on humans

Some latched onto humans, absorbing their bodies’ nutrients and enslaving humans

Some infiltrated the humans’ cities, disguising themselves as normal human beings while feeding upon human blood to sustain themselves.

In a night, the Human race fell to the bottom of the food chain.

The world had turned into a paradise for monsters…

Sara Fujiharu, the cutest girl in the school, is also known as the 'Seatmate Bully'. Every few weeks, the class seating changes and every time, Fujiharu-san gets a new target. What's her goal? To make the boy sitting next to her fall in love, and once she does, she destroys their heart, crushing their love.

Why does she do this? I still don't know.

It's March 23rd, the day of the seating change. So far, ten boys have fallen for her traps, her playful attitude, her innocent face, not a single boy so far has managed to brush off her attacks-and every single time, their weak hearts have been crushed.

Now it's my turn.

However, my heart is not so easily played with.

Quinn Winter is a young man from another world. One day, he is suddenly chosen to become the new Demon King. But the Demon Kingdom is in big trouble – it's losing a terrible war against the human kingdom called Gran'le.To help his people, Quinn comes up with a risky plan. He will sneak into Gran'le and learn their secrets. But things don’t go as planned. A powerful noble sponsors him, and he ends up joining Heavenward Academy, the top school for training future heroes.At the Academy, there's a big challenge called the Selection. The best students become Paladins – magic knights who fight demons. Quinn doesn’t want to become a Paladin. He is a demon king! But now, he’s stuck in the Selection… and if he wins, he’ll become the very thing he’s supposed to destroy.He started the day badly. Now, things are getting even worse.