[Pineapple924]

It seems Toei couldn't help themselves and revealed the new Rider and the Fantasy Buckle in the next episode Preview:



This is Kamen Rider Gyago, he's Seeker's helmet repainted/remolded into a Golden Tiger, and from that description along with the Next Episode summary, is very clearly Kousei (Neon's Dad).

Along with the repaint and mods to Seeker's helmet, he has the Fantasy Buckle which uses repainted Taddle Fantasy armor from Ex-aid. The sleaves, I'm a little less sure of, but probably come from somewhere too.