It Seems That I've Slipped Into a Different World. Also, My Gender Has Changed. - Chapter 69: Being Careful, At Fiance’s Residence

In a world where everyone has a system, Liang Yu, who had lost his previous system, finally received a second one. This time, he was playing the second male lead instead of a cannon fodder.

He has one mission.

Bend the male lead.

Liang Yu: I can do this task just fine. But Lord God, please don’t drop the novel again.

- Description from Novelupdates

When he returned to the World of Martial Arts, the game was filled with blood and battles! Chen Kaixin had chased after the footsteps of the one emperor, two empresses, three princes, seven dukes, and thirteen aces for three years, but during the eve of the Sword Among Us tournament in Mount Hua, he was ambushed by evil bastards, and was killed so much that his level dropped to that of a newbie. He completely lost the chance to join the ranks of the powerful players in the game! In great disappointment, Kaixin quit the game and got drunk so that he could forget his sadness, but during that stormy night, Chen Kaixin found that he had actually dreamed for a total of three years, because when he woke up again, he woke up to three years ago, when he was still a student.

- Description from Novelupdates

As a promise, he went out into the world as an assassin. 3 years later, after becoming the Supreme Assassin, he gave up on everything he had and returned to the ranks of ordinary people. But one day, Kismet, a mystical game created by the National Research and Development had appeared.

Enigmatic hands, spectral frame, and one cunning strike just like the swing of the Grim Reaper. The Supreme Assassin takes on the mystical world, and how his legendary tales sets off, progressively ascending the altar to becoming the best.

- Description from Novelupdates

This world has Fox Fairies, River Gods, Water Monsters, Great Demons and Cultivators who seek immortality.