TTFC's Official Twitter had revealed that someone will make Surprise Appearance in Gaim Gaiden: Kamen Rider Gridon Vs Kamen Rider Bravo. It's still not known who will that be!!
Could it be Kota Kazuraba / Kamen Rider Gaim?
By the way, out of the four known characters → Oren, Jonouchi, Takatora-nii, Jiena-chan, there is one more character which we didn't thought of. Who is the other Kamen Rider Gridon?