(Fair warning: there will be spoilers abound in this series of posts, as I find there are major moments that define some of these characters late in their respective story arcs. So in the event that you have not yet read/watched a particular part of the Jojo’s Bizarre Adventure storyline, you may wish to skip over certain entries.)
#15 - Koichi Hirose: The smallest member of Morioh's trio of main heroes, Koichi Hirose has an undeniably big heart. He seems to dislike conflict, or is at least made uneasy by it, as indicated during his earliest run-in with Okuyasu Nijimura and his antagonistic elder brother. However, when backed into a corner, Koichi will stand his ground and fight for what he believes is just and right. For a kid who constantly displays such a cheerful and friendly demeanor, the stark transition to his fierce battle stances can still be jarring in the late chapters of Diamond is Unbreakable.
Koichi is also rather naïve, finding himself caught up in the obsessive ‘romantic’ advances of Yukako Yamigishi. Being the gold-hearted high schooler that he is, Koichi tries his best to reason with her, despite his general confusion as to why she wants him all to herself, an whether she actually intends to shower him with affection or bring him physical harm. Though he doesn’t really want to, Koichi eventually unleashes his Stand, Echoes, on her agressive medusa-like hair, Love Deluxe. Later on, Yukako decides she would actually like to try and get to know Koichi on a genuine level, and while they are perhaps not head-over-heels in love with one another at the conclusion of Diamond is Unbreakable, they do appear to be on good terms, attempting something of a normal relationship.
As is perhaps most fitting of his personality, Koichi and Echoes do not see nearly as much consistent direct combat with other Stand users as his friend and schoolmate Josuke Higashikata does. He does, however, play a crucial role in the investigation to find Morioh’s local serial killer, and nearly dies at the hands of Yoshikage Kira before Jotaro and his other friends arrive to save him. The way that Koichi, Josuke, and Okuyasu’s personalities play off one another is thoroughly entertaining for Diamond is Unbreakable’s run, and is something that subsequent parts of Jojo’s Bizarre Adventure, given their wildly different settings and generally more serious and intense atmospheres, have never quite been able to replicate.