Koichi Hirose

Koichi Hirose is a key character in the anime adaptation of JoJo's Bizarre Adventure: Diamond is Unbreakable (Part 4). He's a timid, polite, and somewhat meek first-year high school student in the town of Morioh who becomes one of the main supporting protagonists.

Initially portrayed as an average, unassuming teenager of short stature (often depicted as notably small, around 157 cm / 5'2"), with neatly combed light-colored hair (which later spikes up dramatically in intense moments), Koichi starts off nervous and easily overwhelmed by the bizarre events around him. He befriends Josuke Higashikata early on and gets pulled into the world of Stand users after an encounter that awakens his own Stand, Echoes.

Over the course of the arc, Koichi undergoes significant character growth—he becomes much more courageous, assertive, and determined, especially when protecting his friends or standing up to threats. His personality is kind-hearted, honest, and friendly, with a strong sense of justice that drives him despite his initial fears. Echoes evolves through multiple "ACT" forms, giving him increasingly powerful sound-based abilities that reflect his development from someone reliant on others to a reliable ally in battles.

He also has a notable (and often comedic) romantic subplot involving Yukako Yamagishi. Koichi briefly reappears in the early parts of Golden Wind (Part 5) as a more confident young man on a mission in Italy. Overall, he's remembered as one of the most relatable and positively evolving characters in the series' anime version.