Koichi Hirose

Koichi Hirose is one of the main characters in Diamond Is Unbreakable. He's Josuke Higashikata's best friend and ally in the battle against Stand users.

He also returned briefly in Vento Aureo as he was send by Jotaro Kujo to fine out if Giorno Giovanna is good or evil.

Info
Koichi is an amiable but meek youth who undergoes an exceptional degree of character development during the course of Diamond is Unbreakable, becoming more assertive throughout many confrontations with evil Stand users. His greatest leaps are illustrated by the metamorphosis of his Stand, Echoes.

One of Koichi's constant trait is his friendliness. Koichi is a nice person, acting polite toward any stranger and acquaintance, and being happy to help. That friendliness is regularly exploited by Rohan Kishibe to have someone to hang out with. Having a gentle heart, Koichi usually doesn't seek to harm his opponents, notably having saved Yukako from death even though she wanted to kill him before and briefly fighting Giorno Giovanna without the strength to kill, which saved him. However Koichi's friendliness disappears on the rare occasions he is angered, and he becomes more abrasive, violent and vulgar. Koichi also possesses a rather cheerful personality. He finds wonder in the most various facts (his new bike, a famous mangaka living in town, finding an error in a map...), and has little trouble befriending people.

Another one of Koichi's primary characteristics is his courage and associated virtuousness. Heaven's Door exposes Koichi as a cowardly but courageous youth when push comes to shove. True to that assertion, Koichi is very prone to express anxiety, fear and despair at various setbacks, but still soldiers on and braves danger. He takes an active role in the hunt for evil Stand users in Morioh unlike Josuke, being concerned after his encounter with Tamami Kobayashi about what Stand users can do to his family and prioritizes chasing the enemy, which once backfired against Sheer Heart Attack. Initially weak-willed, acquiring a Stand and fighting others made him more confident in himself and assertive, going from being bullied by upperclassmen to facing down and taunting Yoshikage Kira while on the verge of death. By Vento Aureo, Koichi has grown into a totally confident youth.

The mix of these two traits make Koichi an extremely likeable individual, earning the friendship and respect of the vast majority of the cast including Josuke Higashikata, Tamami Kobayashi, Toshikazu Hazamada, Rohan Kishibe, Yukako Yamagushi, Aya Tsuji and Jotaro Kujo.

Koichi is a relatively perceptive individual, able to make quick and decisive moves in a fight, sometimes at the cost of being too imprudent. For the most part, Koichi tries to analyze his situation before acting, notably due to how weak his Stand is at the start of the series and the severe limitations of his powers, but regularly oversees a critical consequence of his actions.

After a difficult start in his relationship with Yukako, due to her kidnapping Koichi, he eventually fell in love with Yukako's tough and unforgiving personality. His love was such that he was willing to be blinded forever in case Yukako became ugly, so as to ease her pain.

Terunosuke states that when Koichi is scared he blinks twice. In addition, Koichi mentions during the Atom Heart Father arc that he has claustrophobia.