Huh, did not realize that. Good stuff. Soichi feels too obvious but definitely a prime suspect now for me alongside Misora and Katsuragi taking this into consideration.

Misora can't be Stalk since She and Stalk have been shown together without Stalk having change of voice like what happened with fake rogue.

I think it's the owner, and Kiryu Sento is Katsuragi with change of face, exposed to Nebula Gas twice, and resulting in Rabbit and Tank gas.

To be fair, Rogue doesn't have a voice modulator like Stalk's and Stalk has a voice actor listed as credited, which Toei likes doing when keeping something secret

Yeah, we see Blood Stalk, Ryuga, Night Rogue and Misora all together in the episode where Misora and Ryuga go out on that date. Rogue goes to abduct her, but Stalk saves her.