Koichi Hirose is a fictional character from the manga and anime series "JoJo's Bizarre Adventure" by Hirohiko Araki. He first appears in the fourth part of the series, Diamond is Unbreakable. Koichi is initially introduced as a timid and insecure high school student, but he becomes more confident and assertive as he gains experience in using his stand, a supernatural ability possessed by many characters in the series. His stand is called "Echoes" and has the ability to create sound effects