The Undead King of the Palace of Darkness (WN) - Chapter 121.1: , The Mirage King (8)

The one single goal in life of the Strongest Old Sage is to subjugate the Demon King. In an epic final battle, both of them met their mutual destruction at each other’s hands.

However, the Demon King was not completely destroyed!

In order to destroy the Demon King once and for all; post-death, the Old Sage trains in the World of Gods and reincarnates as the Apostle of the Gods, Will.

In the reincarnated future, the Old Sage had become a legend and his former disciples hold the supreme authority in the world. The disciples had created an organization to oppose the Demon King and an academy to nurture the new generation of Heroes.

Thus the Apostle of the Gods, Will (8 year old), enrols into that Academy of Heroes.

This is the story of a boy on a mission to save the world through epic battles while enjoying Academy life.

This crossing is so strange, death crossing, game crossing, etc. are probably barely acceptable, but why can you cross even if the fish tank is broken?

and actually passed through the magic tree in “OVERLORD” that is said to be able to destroy the world?

No! It is sad enough to regenerate into a plant. The protagonist, Ainz Ur Gong, the undead king, has also accepted the adventurer’s guild mission and wants to kill me!

I want to change my destiny! Live! I want to-surrender!

Ainz: Since he has accepted the job commission from the Adventurer’s Guild, deliberate failure is detrimental to the prestige of Ainz Ul Christine (the “surrender” button has been deducted)

actually died as soon as he crossed, but there is still a chance to return~ from the beginning of the magic tree to this world.

I must change my destiny this time! Live!

- Description from novelbuddy

A con-man and policewoman that are legends of their respective professions suddenly die, then are reincarnated and return to the Tang Dynasty of ancient China as little kids.

Accepting their second chance and forced restart, they choose to use the modern knowledge and specific talents that they have in their previous lives in order to live comfortably in this new life.

- Description from Novelupdates

A useless prince, yet brimming with kindness and compassion—his smile as warm as sunlight, illuminating this darkened era.But that was merely a mask, hiding the poisonous and mad nature beneath.A monster lurking behind a gentle shell.A system that feeds on stolen Heroines.He will outplay destiny—and rise as the world’s ultimate villain.