Pokemon: The Gameboy Effect - Chapter 12: This Is Love!

Traversing into a Fantasy World, Watson became the youngest son of a run-down baron, ranked eight in the family.

The hearse with the weird odor slowed to a stop before the entrance. The sound of pebbles could be heard bouncing on the ceiling. There were footsteps coming from the corridor, and there seemed to be someone sawing next door. The door knob to the room rattled slightly, and the faucet in the bathroom kept dripping even though it had been screwed shut. There was a rubber ball that rolled on its own underneath the bed. Wet footsteps started to surface one after another on the floor.
At 3 am, Chen Ge held a cleaver in his hand as he hid beside the room heater. The call he was trying to make was finally answered. “Landlord, is this what you meant by ‘the house can be a little crowded at night’‽”

- Description from Novelupdates

The world was once at war with 10 alternate worlds. This was known as the Concept War and our world won 60 years ago. All of this was concealed so no normal people are aware of this fact in the current time.

After the death of his grandfather, the high-school student Sayama Mikoto is suddenly summoned by the giant corporation IAI. He learns this world is headed for destruction due to the acceleration of the Minus Concepts. To prevent this, negotiations must be undertaken with the survivors of the other parallel worlds so their 10 concepts can be released.

And so Sayama is caught up in the final battle to clean up after the Concept War which left behind so much enmity.

After midnight, you’re not allowed to enter the bathroom.

At exactly 2 am, there was a knock on the door.

A woman with disheveled hair and a bony figure always had her back turned to me.

Encountering strange events? Luckily, I can rewind!

This is a story of a reborn individual who navigates a world invaded by strangeness, carefully taking

- Description from Novelupdates