The cast are:
赤 Akaninger / Red / Igasaki Takaharu - Shunsuke Nishikawa 西川俊介
青 Aoninger / Blue / Katou Yakuma - Gaku Matsumoto 松本岳
黄 Kininger / Yellow / Matsuo Nagi - Kaito Nakamura 中村嘉惟人
白 Shironinger / White / Igasaki Fuuka - Yuka Yano 矢野 優花
桃 Momoninger / Pink / Momochi Kasumi - Kasumi Yamaya 山谷花純
Supporting casts
Igasaki Tsumuji - Yashiba Toshihiro is Takaharu and Fuuka's father
Last Ninja / Igasaki Yoshitaka - Sasano Takashi is grandfater of the Igasaki siblings
The names are based on weather theme.
Takaharu = clear skies
Yakuma = clouds
Nagi = calm
Fuuka = windy
Momochi = lands
Tsumiji = whirlwind
Yoshitaka = fine weather
There is a full stories translate from Asahi Page here into English page here.
Akaninger/Igasaki Takaharu will be played by Shunsuke Nishikawa. Nishikawa has practiced Judo for five years.
Aoninger/Kato Cloud Yakumo will be played by Gaku Matsumoto. This will be Matsumoto’s first role as a main cast member.
Kininger/Matsuo Nagi will be played by Kaito Nakamura.
Shironinger/Igasaki Fuka, who is the sister of Takaharu, will be played by Yuka Yano. Yano will also be acting in her first main cast role.
Momoninger/Momochi Kasumi will be played by Kasumi Yamaya. Yamaya acted as Rumi Komaki in Kamen Rider × Kamen Rider Wizard & Fourze: Movie War Ultimatum and also had a role in Space Sheriff Shaider: NEXT GENERATION.
アカニンジャー
伊賀崎 天晴(いがさき・たかはる)…… 西川 俊介(にしかわ・しゅんすけ)
アオニンジャー
加藤 クラウド 八雲(かとう・くらうど・やくも)…… 松本 岳(まつもと・がく)
キニンジャー
松尾 凪(まつお・なぎ)…… 中村 嘉惟人(なかむら・かいと)
シロニンジャー
伊賀崎 風花(いがさき・ふうか)…… 矢野 優花(やの・ゆうか)
モモニンジャー
百地 霞(ももち・かすみ)…… 山谷 花純(やまや・かすみ)
Ninninger Trailers:
You can read the pre-official / rumors casting history here
official webs:
http://www.toei.co.jp/release/tv/1204851_963.html
http://www.super-sentai.net/ss2015/index.html