Underdog

Underdog (アンダードッグ) is a manga written by Hashimoto Izou and illustrated by Mibu Robin.

Plot
What is the purpose of your life? To live is just to die? Is life a slow death? Do you even have your own purpose? Nao is a college student with such thinking...yet, reality is cruel to him. Ever since he was a child, he was categorized as a "ghost boy" whose existence was so faint that no one cared about him. One day, after being mentally traumatized by a child in a family restaurant, Nao snapped and poisoned that child. While being interrogated by the police, a mysterious beauty appeared and rescued him. Her reason was simple: "do you want to dominate the world with me?".