Koichi Hirose is one of interesting supporting character in JoJo's Bizarre Adventure: Diamond is Unbreakable. He is good friends with Josuke Higashikata and always helps him through various problems and dangerous situations.
Koichi possesses a very unique Stand called Echoes. Unlike other Stands, Echoes evolves over time. For more information, check out the following discussion!
Egg Form
When it first appeared, Koichi's Stand was simply a large egg. It awakened after Koichi was stabbed by a Stand-awakening arrow. Because he lacked fighting spirit, he should have died immediately.
However, Josuke healed Koichi with Crazy Diamond's abilities. Because the Stand was only an egg, it was extremely weak and useless in battle.
ACT 1
Echoes ACT 1 has a green, larva-like form. It evolved during Koichi's battle against Tamami. Unlike the previous egg form, ACT 1 has special abilities, although their effects are minimal.
Echoes ACT 1 can write words to a person. These words can be onomatopoeia like those found in comics or written. Furthermore, the words buzz and resonate within the target's body/head.
ACT 2
Echoes evolves into ACT 2 when Koichi engages in a conflict with Yukako. Echoes, originally a larva, takes on a humanoid form. The Stand also appears to have shell-like armor.
ACT 2's powers are similar to ACT 3's and are related to sound. The difference is that the words produced by ACT 2 can have a more tangible effect when touched by someone. For example, the word "FWOOSH" can generate a strong wind.
Other examples include "BOING," which can make objects elastic, or "SIZZLE," which can produce a burning effect. Another ability of ACT 2 is its significantly increased speed.
ACT 3
ACT 3 is the final and most powerful form of Koichi's Echoes. When it evolves into this form, Echoes ACT 2 takes the form of a metallic humanoid robot. It can also communicate with Koichi.
Echoes ACT 3 possesses a powerful ability called 3 Freeze. This ability allows Echoes to increase the weight of a target by striking it. According to Kira, the resulting weight is in the range of 40-50 kg.
While Echoes ACT 3's abilities are powerful, there are limitations. For example, 3 Freeze can only affect a specific target at a time. Furthermore, its effect depends on the distance between the target and Echoes.