Катаґірі Юїчі

Yuuichi Katagiri is a hardworking lad who believes friends are more important than money. In reality, he is a dead broke student with multiple part-time jobs. In secret, he is "the mind" of the team, and often, even when things seem dire, Yuuichi manages to swing the odds to his favor with every ounce of his might. His past is heavy--and often, for it, he is called a "devil" and considered dangerous.

In Chapter 99, it is revealed that Katagiri Yuuichi is the one who created the prototype for the "Tomodachi Game".