One Piece: Supreme Check-In System - Chapter 59: One Blade vs A Hundred Storms

The king of assassins was reborn, mastering both alchemy and poison. Sitting inside the space, there was a ghost that loved crying.

Buying a sickly boy for a hundred gold coins, becoming the master of half a country for no reason.

On their wedding night. She slightly hooked her jade finger, “Come here.”

The man tried weakly bargaining, “Can I redeem myself?”

“No!”

“Can we wait for the bridal chamber tomorrow?”

She cast a cold gaze, “Give me a reason.”

“I…..My period is here.”

Her head was covered in black lines, “Do you think you would even believe that!”

After four hours——

She weakly said, “I can’t go on anymore, wait until tomorrow.”

The man revealed an evil charming smile and turned her over before pressing down, “Want to run? Too late!”

- Description from Novelupdates

This legend tells the tale of the protagonist, Kuroki summoned to protect the demon king from the hero.

Kuroki, unbeknownst to him, suddenly came to another world. He was summoned by the demon king, Modes. The territory which the demon king overrules was in the midst of being destroyed because of the hero. He had no choice but to bow before Kuroki.

“Please save us, Savior Dono!”

Kuroki nodded, deciding to save the demon king due to an unexpected turn of event.

Shen Zhixian transmigrated into a book as a cannon fodder master who hatefully severed his disciple’s spirit root. This disciple fell into the devil’s path and returned to make mincemeat out of him.

Shen Zhixian just happened to transmigrate into the last moment of the master’s captivity, and then he was reborn again.

After rebirth, he devoted himself to fostering and supporting his disciple, only to discover later that his disciple was also reborn.

Even worse, the disciple still retained the memory of his life before rebirth.

Shen Zhixian: …Disturbed.

Afterward, he realized one truth: Being a master is a high-risk occupation. Not trivial at all!

- Description from Novelupdates

The story is about a a hitman, Who dies because of his own recklessness and transmigrates into a game he used to play after his retirement as a hitman.I'm not gonna spoil any further, but i might answer few of your questions.Is MC overpowered?Nope, he'll become strong over time and all battle he'll fight will be because of his effort and techniques.Is there magic and adventure?Yes! It have both magic like normal isekai with adventure and fighting with monsters and many other things. There are other important things like “Essence Stone” But let's talk about it in the chapters.There will be harem?Not really, He will be in contact with many beautiful female and males but one waifu but i haven't decided yet.All i can say is, give it a try, I'll try my best to make it worth your time.