City of Sin - Book 1, Chapter 11

In the rebirth, in order to prevent the tragedy of the previous life from happening, Bai Yu decided to rush to the [Tower of God] at any cost, and face everything together with his sister!

However, Bai Yu, who was bound by the system, mutated his bloodline, and transformed into a black-scaled python seems to be developing on a completely different path from his previous life…

- Description from novelbuddy

The previous life is nothing but a joke. Being used completely then abandoned mercilessly. How can I be this stupid to not even notice such an obvious scam? Fortunately, I can have a second chance with my rebirth. Sister, Brother Yi and whoever mistreated me in my previous life, are you ready for my revenge and the counterattack of a princess?

The fat and ugly Nora Smith is the laughingstock of the town when her fiancé breaks off their engagement.

Junpei Takeda, a high school student, is childhood friends with Noriko Tatsumiya and is bullied by Kido Shouta. One day, while bullying Junpei, they (Junpei, Tatsumiya, & Shouta) were suddenly summoned to a different world by the whim of “God”. Summoned Heroes with cheats, or so he thought. But it turns out Junpei’s stats were even worse than an average farmer. Tricked into a deathly labyrinth by the only one he trust, he walks the journey for revenge.