Isekai Maou to Shoukan Shoujo no Dorei Majutsu - Volume 7 Chapter 1 part4

Every drop of this family bloodline is stained with sin. They are the embodiment of contradiction; calm yet maniacal, with great memories yet often forgetful. They pledge themselves to their dreams yet often compromise, are angels that are also devils… It’s why I hate them. And also love them.

The only hope of his family, a youth with the blood of elves and devils walks on a battleground of annihilation and rebirth. He wills his way through boiling lava and icy depths, killing on this field of despair to strike down the lofty figure in his sight. One day he’ll grasp his blade tightly and survey his surroundings, only to find no more enemies to kill.

Our straight (?) bottom woke up ten years into the future and found himself on the bed of his childhood friend… At the start, the bottom was shocked to his very bones, but he soon quickly accepted this premise and found the whole situation to be rather amusing. Precisely then, the bottom once again went back to his timeline — back to when he and the top were just platonic childhood friends.

Kurt was born to a poor Baronetcy of Arnold. He was a genius pastry chef in the previous world.

In novels with a stud there is always a Senior Martial Brother like this:

In the early stages of the novel, his innate talent is high, his cultivation is good, his appearance is handsome, and he has an intelligent, cute younger Martial Sister as a fiancée.

In the middle stages of the novel, he is caught unprepared and defeated by a young disciple (the protagonist) in the sect who’s hardly remarkable at all. From then on, he falls from his godly altar and loses his brilliance. Even his young Martial Sister leaves him for someone else.

In the late stages of the novel, he continues to turn dark, going down the Demonic Path and becoming the major villainous boss. However, the protagonist still ruthlessly defeats him and his soul is eternally sealed.

Once Qin Mo opened his eyes, he discovered that he had become this Senior Martial Brother.

- Description from Novelupdates