Kamen Rider Kaixa (仮面ライダーカイザ, Kamen Raidā Kaiza, Masked Rider Kaixa) or SB-913 Kaixa (SB standing for Smart Brain) is the secondary rider of Kamen Rider 555. Its gear is the second of the Rider Gears seen in the series. Its motif is the Greek letter chi (X).