Who is Reigen?

Arataka Reigen is the self-proclaimed Spirit Counselor who runs Spirits and Such Consultation Office. He has no psychic powers. He hired a twelve-year-old with world-ending psychic abilities to do the actual exorcism work while he takes the credit and the money. He is a fraud, a con artist, and also genuinely the best mentor Mob has ever had.

How does a fraud become a great mentor?

By being present and consistent. Reigen always shows up. He praises Mob's effort, even when the effort is just being a decent person. He gives advice that is surprisingly often correct (mostly about not using violence to solve problems that aren't violent problems). And he genuinely cares about Mob in a way that isn't strategically useful to him — the caring costs him, which makes it real.

What is Reigen's most important piece of advice?

"You are 100% human. Never forget that." Said to Mob when he's struggling with his identity as an esper. Reigen, who has no powers, is telling the most powerful esper in the story that the powers are not the point. Coming from someone without the thing he's minimizing, the advice lands differently.

What does Mob give Reigen?

Meaning. Reigen was a con artist going nowhere until Mob arrived. Whatever he says to the cameras, Mob is the thing that makes his work real — the thing that means he's actually helping people rather than just performing helpfulness. Mob's trust in him is also the standard he has to try to meet.

What does their relationship teach about mentorship?

That you don't have to be the strongest to mentor effectively. You have to be present, honest about what you know and don't know, and genuinely invested in the other person's development as a person — not just as a skill-set. Reigen fails at some of this and succeeds at enough of it to matter.