Echoes
Unlike most other Stands, Echoes has three distinct forms, or ACTS (Koichi can only call upon one at any given time). Echoes [ACT 1] resembles a flying (although wingless) turtle with a long tail and wheels surrounding its beak. Its power is to write a given sound effect in kana on a surface. The effect will then constantly sound with increasing volume, until Echoes dispels the writing. Until his confrontation with Yukako, this was the only Act that Koichi could access.
During that battle, he gained access to Echoes [ACT 2], which has a more humanoid form. Rather than just making sounds, Act 2's tail can create sound effect writings that actually invoke the associated quality when activated (e.g. if "whoosh" is written, activation will create an actual wind current).
Finally, during his first confrontation with Kira, Koichi discovered Echoes [ACT 3], a completely humanoid Stand with turtle shell-like bosses on its body (and a somewhat independent, foul-mouthed personality who quotes Bruce Willis from Die Hard). Unlike the first two Acts, Act 3 cannot fly, and has a much shorter active range. However, it is extremely fast, and can FREEZE any one thing within 2 meters by rapidly punching it, at which point the object will suddenly become extremely heavy (it even caused Sheer Heart Attack to sink into solid pavement).
The user is Koichi Hirose, and its name is based on the song by Pink Floyd, Echoes. [1]
