Research? uh-huh. Riiiiight.

Rika Nanase (Zonnette in Gekisou Sentai Carranger)
Asami Jo (Shibolena in Denji Sentai Megaranger)
Kei Mizutani (Shelinda in Seijuu Sentai Gingaman)
Nao Oikawa (Kegaleshia in Engine Sentai Go-onger)

Also, not really porn, but Rei Saito (Tsuetsue in Hyakujuu Sentai Gaoranger) released a nude photobook shortly after the series ended. Reiko Chiba (Mei/Ptera Ranger in Kyouryuu Sentai Zyuranger) posed nude in some of her photobooks as well.

On the Kamen Rider side, Reon Kadena was an AV idol before playing Eren Komori in Kamen Rider × Kamen Rider OOO & W Featuring Skull: Movie War Core.

In other toku, Aya Sugimoto (Queen Beryl in Pretty Guardian Sailor Moon, Maria S. Cranberry in Kamen Rider W Forever) released several nude photobooks, posed nude for a PETA ad, and starred in the softcore porn film Hana to Hebi (Flower and Snake). Naomi Morinaga (Annie in Uchuu Keiji Shaider) resorted to B-movies and nude photobooks when her career went downhill.

Somehow I'm not surprised by the last two.

It's bad when other people start to notice :lol
I'll wish with you.

Agreed, she's actually really good at the part and pretty entertaining aside from being super hot.
Yeah, sure, reasearch.
Yeah, sure, research :)

We've been pretty lucky to get all of the Akibarangers as regular releases, but I don't think there's even a slim chance Malshina will be.