More rumors circulating the secondary Rider has just surfaced the net! Someone posted on 2ch, a popular Japanese online board has just posted rumors about this secondary Rider.
The second Rider's transformation gun. Includes 3 O Medals that are put inside to transform. By putting in various medals you can change forms and even activate a special attack. The Cell Medals to activate special attacks are sold separately.
Aside from that, according from a reliable source, these medals are: Kabuto, Hachi (Bee) and Donbo (Dragonfly).
Until Toei confirms it, take this as a grain of salt.
Source: Hobby Net via DecaEnd, Gold Samurai
About the rumored medals, is it me, or it screams like it came from Kamen Rider Kabuto?