Jiro turns into a blue wolf in a different way now.
Leo's father in Makai Senki is played by Daisuke Ban, perhaps better known as the eponymous heroes of both Kikaider and Inazuman.
Ganon's humanoid form is played by transvestite actor Shinnosuke Ikehata AKA Peter, who was famous for playing Kyoami, The Fool in Akira Kurosawa's Ran.
In the third season, Jakuzure Takeru/Flame Blade Knight Zen is played by Junya Ikeda AKA Gai Ikari/GokaiSilver.
In Yami o Terasu Mono, The Dragon, Sonshi is played by veteran martial arts actor, Yasuaki Kurata. He's famous for starring in films such as Fist of Legend opposite Jet Li and Heroes of the East opposite Gordon Liu. And this isn't his first toku either, having played Akashi Kouichi. With a pedigree like that, he easily curbstomps the heroes.
The powerful Horror who served as a MacGuffin in Makai Senki is named Ganon.
The new character from the Soukoku no Maryu movie is named Kakashi.
You Look Familiar: The theme park manager from Episode 10 of the 2005 series (who harasses Kaoru) shall later on play Ratess in Makai Senki.
The new character from the Soukoku no Maryu movie, Kakashi will be played by Yuki Kubota, who previously played the obnoxious idol/actor JURAN in episode 9 of Makai Senki. He was the episode's Victim of the Week.
And now, Kouhei Otomo, who played Igari Juzo in Makai Senki is playing Burai, the old Makai Priest in the 3rd season.