MMO: Pierce Heaven Til' It Breaks - Chapter 924 - Heaven on Earth

The strongest Demon Lord dies, and reincarnates as a human. Not only that, he because of various incidents turns into the hero’s best friend.

Follow his journey as he tries to help the hero escape his fate, and on the sideline to conquer the continent while he’s at it.

Jerry traversed across worlds and arrived in a Beast Summoning era. In this world, everyone could summon their own pets. Darkness was looming, and the world was in turmoil. Relying on the power of their summons, many shrines plundered the resources at every corner of the world like tyrants. But when everyone else was summoning adorable pets that could help them in battle, Jerry discovered that his summoned pets were a little different. Other people's pets are all kinds of beasts, but Jerry summoned gods from Greek mythology! King of the Gods, Zeus, “Master! I, Zeus, is at your command!” Athena, “I will fulfil all your requests, master!” Poseidon, “I will conquer this sea in the name of the master!” In constant summons, step after step, Jerry became the supreme ruler of this world!

The end of the world is coming, the world has undergone great changes, and everything has changed. Plants, animals, and even insects, as long as there are living things, have mutated.
Become more powerful, and even evolved supernatural abilities, such as chickens and ducks that can fly to the sky, such as cats and dogs that can breathe fire.
But only humans, without any obvious changes, seem to have fallen from the top of the food chain to the bottom of the food chain overnight.
Any creature that can open its mouth to eat can treat humans as food.
But fortunately, this world has not completely killed humans. Gradually, humans discovered that they had the ability to cultivate compatibility with other creatures.
As long as it has a high degree of compatibility with some powerful mutant creatures, it can be used for its own use to achieve the purpose of protecting itself.
Fang He is a person who is very compatible with mutant animals, but it is also because of his ability that he has changed from the strongest to the stupidest.
Fang He, who was reborn, said, “Hmph, this time…”

- Description from novelbuddy

Utsuro no Hako to Zero no Maria, or The Empty Box and The Zeroth Maria, tells the sinister story of Kazuki Hoshino, who is almost madly attached to his everyday life, and his antagonist Aya Otonashi, who suddenly transfers into his class—for the 13,118th time. She majestically announces to “break” him, without paying heed to anyone else around them.