Komagine Kiita as Kaito Goshikida / Zenkaiser
Komagine Kiita 'K.K.' is going to play Kaito Goshikida / Zenkaiser. He wants to become No.1 in any field. Normally he is loose and bright 'Baka', but when he switches up, he becomes Hot Headed 'Baka'. His catchphrase is "Secret Power! Zenkaiser!". He is the alumni of the Love Reality Show 'Ookami Series' from which we got Fumiya Takahashi (Kamen Rider Zero-One), Hikari Kuroki (Yuka Ohta in Ultraman Z) & Takaya Yamaguchi (Kamen Rider Blades)
Asanuma Shintaro as Juran / Zenkai Juran
Muscle type Kikainoid. He is confident that he is cool and trendy. But from other's point of view, he is just an irritating old man. His catchphrase is "Kyoryu Power! Zenkai Juran!".
Shintaro Asanuma had previously the voiced Shadow Seijin Zena in Ultraman Geed.
Yuki Kaji as Gaon / Zenkai Gaon
Even being a Kikainoid, he loves the creatures of earth than machines. A natural and innocent Kikainoid. He considers Kaito as a pet. He is good with cooking. His catchphrase is "Beast Power! Zenkai Gaon!". Yuki Kaji is known for his role of Eren Jaeger in Attack of Titan Anime.
Yume Miyamoto as Magine / Zenkai Magine
An introvert type Kikainoid. She lives fortune telling, Fantasy and Occult. She gets angry when someone makes fun of things which she likes. She is bad at organizing. Her catchphrase is "Magic Power! Zenkai Magine!".
Yume Miyamoto had previously voiced Rikka Takarada in SSSS.GRIDMAN.
During the press conference Zenkai Magine said "Past Super Sentai won't appear". I wonder if she was joking or did she really mean something?
Takuya Sato as Vroon / Zenkai Vroon
He is pretty serious like a class representative. He irritates everyone by asking questions when he is curious about something. He likes to keep things clean and organized. His catchphrase is "Rumbling Power! Zenkai Vroon!".
Ikue Sakakibara as Yatsude Goshikida
She is the grandmother of Kaito and also the owner of Sweets Cafe "Colorful". In the trailer revealed at the press conference, Yatsude was seen holding the Geartlinger along with Kaito.
Ikue Sakakibara had mentioned that she is interested to transform into a Sentai even though it's not in the script now. Looks like Toei will make her wish come true. Maybe in the future episodes.
By the way, she is 'Everyone's Idol' teased earlier and also the initials "S.I.".