Keisuke Soma who had previously played Genta Umemori / Shinken Gold in Samurai Sentai Shinkenger is returning back to Tokusatsu after 11 years. He is going to appear Kamen Rider Saber Episode 23 as a Soldier of Southern Base.
He will confront Touma who had infiltrated inside Southern Base. He is seen with a brown colored Wonder Ride Book. What will that do?
By the way, it's not confirmed whether he is a Guest Star or a Regular cast yet. But since it's also not mentioned anywhere that is a 'Guest', there is a high chance of him being an key regular character.
There is a chance of him being one of the remaining two Riders.