Rakuin no Monshou - Volume 12, Afterword

A modern-day antihero, who was infamous for his devious acts, dies in an explosion meant to take down a powerful criminal syndicate. Waking up in a world of sword and sorcery, he finds himself possessing a fragile, powerless body with a strange “System” that seems broken. Initially thinking he's doomed, he learns that by pretending to be weak, he can manipulate others into revealing their secrets, granting him abilities they possess. As he rises in power, he discovers that the System was intentionally sabotaged—by none other than his own future self.

A part-time job contract. He became the cold CEO’s imitation boyfriend. He merely wanted to earn a few small bucks and live a comfortable life, but a pity, he was in constant turmoil since then. Well, life had something else for him despite his wishes.“That… beauty, will there be an increase in wages for conversion from ‘boyfriend’ to ‘husband’?”

- 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.

She never dreamed that she would meet him in the bathroom and they...Five years ago, she betrayed him for some reason and chose someone else, which deeply hurt him and he swore to make her pay the price. After the reunion, he launched a fierce attack on her, while she tried to escape this emotional entanglement.However, the red line of fate seems to have already tightly connected the two. Through repeated interactions and confrontations, they gradually uncovered their past misunderstandings and got to know each other again. His deep affection for her remained, and she was gradually moved by his sincerity.