Kamen Rider Aqua
A Rider from the future. Arrives in the movie Kamen Rider x Kamen Rider Fourze & OOO: Movie Taisen Mega Max.
Played by Arai Atsushi.
Ironically, Miharu hates the water. This is why he relied on the future Medals to turn into Kamen Rider Poseidon, but ended up being unable to control that Rider. Eventually, he gains the confidence to fight and helps Eiji before returning to his own time.