Koichi has an easy-going, mild-mannered personality. He is very generous and does not seem to expect anything from other people in return. He is somewhat unaware of social clues, accidentally gaining a reputation of being a "creepy guy", both among his peers at university, and as The Crawler. He also often accidentally insults people when trying to compliment them; he can be very awkward.

Age 19 is recommended for this role but not mandatory!