A Hentai System in the World of Danmachi - Chapter 40 - 39 - Contract and dinner.

A generation’s War God, once overlooking the world with disdain, had fallen into disgrace because of a conspiracy, becoming a mere son-in-law. However, what nobody had expected was that it was all part of his grand scheme, and when the winds of change blew, he, the king, returned, with the power to overturn seas and move mountains, as a dragon ascended to the heavens!

My handsome, overpowered dad, who only ever cared about me, ate something strange and turned into the Demon King. He used to be the sweetest, most doting father, but now he’s the final boss?! Because of this, my dad is fated to be killed by the male lead, and I’m destined to die lonely while mourning him. At that moment, I returned to the past and realized that this world is actually a game! I couldn’t prevent my dad’s descent into darkness, but no matter what, I must turn him back into his original self. If I succeed, I can get my loving dad back, right? For now, I need to get close to the male lead, who’s destined to kill my father…! So, I became a Holy Knight and even managed to be adopted as the ward of the Pluto Ducal House—the male lead’s family. …The problem is, I’ve become way too strong. As long as I get along with the male lead, my dad might avoid being labeled as the Demon King. “But that’s strange.” “…What is?” “Your lips… they’re heart-shaped.” “W-what? Don’t look at my lips!” At that, the male lead tried to avoid my hand and ended up rolling under the bed. “Ahhh!” “…?” He’s supposed to be the strongest person who’ll one day kill my dad, but for now, the male lead is just too cute.

Lu Zhengfei personally killed Chen Qianqing with his abuse.

He cut off Chen Qianqing’s legs, and blinded his eyes, locking him up with chains in his house. Then, he watched with his eyes wide as he died. Injuries inflicted in the name of love would always end in a tragedy.

Did Lu Zhengfei regret it? Of course he did. And so, God gave him a chance to be reborn.

But this time, he found that he himself——became Chen Qianqing.

- Description from Novelupdates

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.