[Sunred]

Zenkaiger cast
Kaito Goshikida/Zenkaiser by Kiita Komagine
Zyuran/Zenkai Zyuran by Shintaro Asanuma(Alien Shadow Zena voice from Ultraman Geed)
Gaon/Zenkai Gaon by Yuuki Kaji(Eren Yeager from Attack On Titan)
Magine/Zenkai Magine by Yume Miyamoto(Rikka Takarada from SSSS Gridman)
Vroom/Zenkai Vroom by Takuya Sato(Caesar Zeppeli from Jojo's Bizarre Adventure)
Yatsude Goshikida(Kaito's grandmother) by Ikue Sakakibara (veteran recording artist)


Here is the quick rough translation of their bios from the TV Asahi website from yours truly.

Kaito Goshikida/Zenkaiser: Though not skilled in any area of expertise, always aims to be "the world's first". Carefree and goofy most of the time, when serious he becomes a hot-blooded fool.
Zyuran/Zenkai Zyuran: Although he considers himself the cool old guy type, he is in reality a very loud and stubborn old man. A power type kikainoid from head-to-toe.
Gaon/Zenkai Gaon: A ditzy kikainoid who loves lifeforms of Earth more than machines. He even considers Kaito a pet. Loves cooking.
Magine/Zenkai Magine: A shy kikainoid who loves fortune-telling, fantasy, and occult things. She is quick to anger if the things she like are made fun of. She is horrible at organizing.
Vroom/Zenkai Vroom: The serious academic type, this kikainoid is very curious and will not stop talking about the things he likes.
Yatsude Goshikida: Owner of the dagashi cafe Colorful and Kaito's grandmother.