Izumiya Kazuki is Hirosuke's buddy at school. During summer he works in a flower shop (and wears a straw hat when delivering flowers to customers).

Kazuki is quite busy dating various girls but with no lasting results so far. Kazuki encourages Hirosuke to confess his feelings to Yasuna but he also talks him into joining him to a four-way date with two "college girls", one of them being Suzue.