MTL - Quest Master of Konoha - Chapter 418 energy fusion

After a disaster, a despised son-in-law quietly undergoes a shocking transformation. With both medical and martial arts skills, a battle for redemption is on the brink of erupting...

In all my life, I’ve only made two mistakes that I regret. The first was filling out my entrance exam application wrong, and the second was offending Zhong Yuan. If I had to use an idiom to describe the impact of my mistake, it would be simply, ‘Life is no better than death’. And if I had to use an idiom to describe Zhong Yuan’s offenses to me, it would be simply, ‘Too many crimes to record’. And yet, for as evil and wicked as he was, he attracted girls the way that flowers attracted bees and butterflies.

It happened that one day, for some reason, I taunted Zhong Yuan, “The King of Hell sent you to torture some more people, didn’t he?” Without a change in expression, he replied, “In order to torture fewer people, I decided to just choose one person to torture for the rest of my life.” I asked him, “What do you mean?” He smiled at me and answered, “If you don’t go to hell, who will?”

- Description from Novelupdates

On his usual way to home Mikado Tsuchio fell into a hole that suddenly opened on the ground. Just like that, Tsuchio falls in a different world, he lands on a Grappler Wyvern and manages to tame it.

Tsuchio decides just like that to live in the other world, the reason for his quick decision: he wants to make a monster girl harem.