Now that the subtitled version is out, I can talk about it freely without spoiling. If you were curious what Akibaranger was referencing when I posted about Mitsuko Horie last week, feast your eyes and ears. Akibaranger was referencing a tokusatsu show called Ninja Captor, a non-Sentai ninja series with a well loved theme song performed by anime and tokusatsu song legends Ichirou Mizuki and Mitsuko Horie.
Of course, Akibaranger changed it very slightly to Ninja Cap-tan, a magical girl ninja themed ninja series, and Mitsuko Horie was herself using a pseudonym, but the theme music is note for note identical to the original, though the lyrics have been changed.
The series ran from 1976 to 1977. Shotaro Ishinomori was not involved in this series, but much like the original Kamen Rider and Kamen Rider Stronger, it features a hero who escaped from an enemy organization and used their powers against them. The difference is, in this series, the hero has a team to back him up.
While not a Sentai series, Ninja Captor featured elements common to the series, and was listed as created by Hatte Saburo. Officially, it is classified as a "Ninja Hero" series, but not alongside Ninja Sekai Sen Jiraiya, which is a Metal heroes Series. Actually, it's kind of nice that someone mentioned Ninja Captor at all, since unlike other entries into the various series (such as Gavan, Sharivan, and Shaider, Poitrine, and Inazuman), Ninja Captor has not appeared in any crossovers with other Toei properties to date.