After Switching Bodies, the Mad Overbearing CEO Takes Over the Entertainment Industry - Chapter 18 - summarized very well, don’t summarize next time

In the new era when the earth began the test to become a Level 2 Civilization, everyone's Constellations played the most important role because only from them could people obtain skills.Having a contract with a stronger Constellation meant getting skills with a higher class.Money was the determinant of getting stronger Constellations as they offered skills to those who paid more.Oliver had no problem with that as he was raised by his aunt who was a super rich woman.That woman could contract one of the Strongest Constellations.However, she suddenly offended the Constellation she was about to contract, causing an inevitable conflict.As a result, that Constellation used his influence to make all Constellations not accept contracts from the two of them.Even with a lot of money, their status was destined to plummet in this new era if they did not have a Constellation.They had to be prepared for the attacks of their enemies.Unexpectedly for Oliver, when he felt hopeless, he accidentally joined a chat group that he initially thought contained strange people but turned out to be the most powerful figures in the universe.Even two of them casually gave him SSS+ Class Skills...

A fickle, decadent, wilful person going through life like it’s a game.

An experienced, logical mind that’s above feelings.

This was a relationship that had started off with “Carpe Diem”, but slowly turned into a bloodless, psychological battle. They shared a mutual distrust, but also mutual attraction. As they suspected and tested each other, challenging each other’s limits, they both fell into the enemy’s hands with their eyes wide open. Sentiments growing amidst ignorance, they finally, were caught in their own traps.

Winner takes all,

Loser stands small.

- Description from Novelupdates

The only way to stop the earth’s doom.Is to seduce the girl who is the student council president.

Lyle Walt is a young noble boy and heir looking forward to the day he can inherit his family’s territory. Except around when he was 10 year old, his parents started neglecting him more and more in favour of his little sister, Celes.
On his fifteenth birthday, he is challenged to a duel by his sister to see who will inherit the household and horribly loses, being cast out of his family. Afterwards, he gets treated by the family groundskeepers and receives the family heirloom Gem from him that Lyle’s grandfather had entrusted to him. From there, he begins an aimless journey with his childhood friend and former fiancée, Novem, and the Gem-turned-Jewel that houses the memories, personalities, and Skills of seven of his ancestors.