Ishikawa-sensei is a minor but memorable character who appears alongside the fifth-grade teachers at the school where the main story takes place. He is most likely the physical education instructor for that grade level. His physical appearance is quite distinctive, as he is consistently seen running around in a jumpsuit, with messy hair, a beard, and glasses.

Regarding his personality and role, Ishikawa-sensei is a source of both practical knowledge and questionable behavior. On one hand, he occasionally assists others by offering advice and sharing spiritual information based on his own experiences and what he has learned. On the other hand, he is also described as something of a bad influence. This is highlighted by his habit of keeping cards for various adult shops stored in his jumpsuit, a fact that the protagonist Nube discovers accidentally when the cards fall out of a suit he borrowed.

Ishikawa-sensei also exhibits several peculiar personal habits. He has a notable tendency to avoid showering for extended periods, sometimes for more than a month. Furthermore, he has a fetish for wearing women's undergarments. This particular trait once proved to be problematic, as it worked against Nube when a character named Minki, the sister of the demon hand Baki, came from Hell to reclaim them. No further information is available regarding his background, motivations, key relationships, character development, or notable abilities beyond these described quirks and his secondary role as an occasional advisor.