With Mangekyo, I Escaped Konoha To Other Worlds [Naruto/AttackOnTitan] - Chapter 16 - 15 The Aftermath

[Mc takes consent from Woman not their husband][Mc doesn't want to NTR every guy. He only makes their wife cheat for sex.][Making friend's mom fall......is one of his big dreams.]“I like married women and there are so many noble women out there...”A horny Otaku from Earth gets transmigrated as an old Viscount.His lifespan is depleting too quickly due to an injury.Fortunately, there is a Ying Yang technique which can increase his lifespan.“This man has been single for his whole life and never touched a woman? WTF!!” Otaku is shocked from the Viscount's dry life.“I do have the maids, right?”[MC likes married women][Netori, Cheating, Blackmail]

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

An ordinary (?) grandfather, Choi Chuntaek. In an effort to protect his granddaughter, he started the virtual reality game 'Arkstar.'

Then... he accidentally obtained a legendary class?

Intelligence without ambition is like a bird without wings.