It is strange, but there have been quite a few toku actors whom I got curious about and when I digged, turned out that they had been in the Prince of Tennis Musicals. I know I'm probably missing a few, but I'm just going to list the ones I cared enough to find out. Please note that I do not necessarily follow each actor's career.
Hiroki Konishi (who changed his name to Ryousei Konishi, but I'm listing his old name because that's the name most people are still familiar with) as Shinji Ibu (Fudomine)
He played Kouga Saejima in GARO.
Sota Aoyama as Sadaharu Inui (Seigaku)
He played Kaito Touma, the human who bonded with Ultraman Max.
(I was never curious about Aoyama actually, but I found out about his connection with tenimyu when I searched for Konishi's past work, and since I watched Ultraman Max, I might as well include him on this list.)
Kazuki Kato as Keigo Atobe (Hyoutei)
Most people probably already know that he played Daisuke Kazama in Kamen Rider Kabuto.
Ryunosuke Kawai as Wakashi Hiyoshi (Hyoutei)
He played Jun Suzaki, a childhood friend of Konomi Amagai (one of the female Crew GUYS members) in episode 28 of Ultraman Mebius.
Also Kawai is starring as one of the heroes in a straight to DVD tokusatsu show called Zan Saber, apparently made (or at least distributed) by the same people who did Evolver. Since I liked his acting well enough in Mebius (not to mention his character was one of the only few people who managed to cause the usually sunny Mirai to lose his temper), I would probably buy the DVDs for this show.
As a side note, Mirai Hibino, the human form of Ultraman Mebius, is played by Shunji Igarashi, a member of D-Boys. While Igarashi has never been in tenimyu, most of his fellow D-Boys members have performed in the musicals.