Susumu Nakoshi is a middle-aged man living in his car. Spending his time between a park full of homeless people and upper-class complex hotel, he is chosen by Manabu Ito to be an experimental guinea pig because he is neither an egocentric wealthy guy, nor a pitiful homeless man. He is "just between".

After the Trepanation he is able to see the "monster" in each human being, things that frighten or obsess people. By studying the human nature and facing the other's fear, he'll try to understand his own person thanks to this strange and worrying 6th sense.