I don't think that this is a Sengoku Rance doujin... that Shingen is much closer to his Sengoku Basara version than his Rance version (which is merely an empty armor. Not even Sengoku Basara's expy in Sengoku Rance (Baba Shouen) looked like that.). On a more nitpicky note, Sengoku Rance's Kenshin does not wear that kind of helm; hers is a tall, more-or-less conical helmet.

I think this is a Sengoku Basara doujin with a genderswapped Kenshin, or a crossover.