Fukujiro Yasunaga

First appearance: Chapter 1
Name revealed: Chapter 77

The 53-year-old Japanese history teacher who is also Kenichi's homeroom teacher. He and Kyōko Ono pay a visit to Ryōzanpaku to check out rumors that Miu is living with another student although the misunderstanding is eventually cleared up. He is a huge fan of Koetsuji's work and refers to him as sensei.

His shiny bald head is commonly used on jokes, such as when Niijima recognizes his head through its shine from far away while seeking help after himself, Kenichi, Miu and Tanimoto get lost during their school trip to the snow due to Jihan's attack.