Villain – Peeking at the Diary, the Female Leads' Personas Collapse - Chapter 59

Lee Jung-ho the former minister of finance for South Korea, got assassinated and reincarnated into the duke family as a young child named kaidënHe felt the love and care he never felt in his past life, as all he want his just to live a normal average lifeBut things don't go as planned as he starts to draw attention to himself due to his mana type and his weak potentialBut with just a some basic science, one can change the world, at least that happen for kaidënJoin the journey of kaidën as is raise is fallen family to the top, through the fight of money, power and magic, plus the demon in him

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

In this period where countless supporting lead actors always attempt to counterattack, turn over a new leaf or simply refuse to take up the role, his purpose of existing is to fill the role of a good supporting male lead and uphold his duty to the best of his ability. To add the needed lustre to storylines and this world. Only, it’s a pity that someone who is not afraid of god-like enemies will be afraid of pig-like teammates.

Bitterly, he realises that for some unfathomable reason, he is being bothered time and again by a bastard who refuses to follow the script… In order to walk the path of a good supporting male lead, he engages in a battle of wits and courage with that person. Loving each other and killing each other, one ultimately cannot escape fate’s teasing– why is it so difficult wanting to be a responsible and diligent supporting male lead?! QAQ

- Description from novelupdates

Hitoshi's life sucked and then a truck made it even worse.But death wasn't the end. He wakes up in a fantasy world as a slave, expecting more of the same bad luck. Then a maid from the super-rich Aoi family buys him to work at their huge mansion. Finally, a break, right?Wrong.Sure, the mansion is amazing. The food is great. And yeah, the Aoi family treats him way better than he expected. But something's... off. Why do they watch him so closely? Why does everyone get weird when he smiles? And why do bad things keep happening to anyone who gets too friendly with him?Hitoshi just wants to be a good servant and make everyone happy. He doesn't realize that his kind heart and helpful nature are stirring up something dangerous within the Aoi household. In this new world, his greatest talent might become his biggest problem.They say no good deed goes unpunished. In the Aoi mansion, every act of kindness pulls him deeper into a web of obsession he never saw coming.“Reincarnated into Madness: Yandere Family's Unwanted Slave” is a story about second chances, magic, and what happens when being too nice leads to some seriously creepy consequences.