1. Muneshige and Ginchiyo may not even be in adjacent Kingdoms! (Kingdoms next to eachother are a big NO)
2. ONLY YOU CAN TRANSFORM IN THE LEGEND OF RANSEI (Toturial Story/"Main Story") ... Which means that you need to try this in the "Poat Game" (Real Game)
3. You must have both Muneshige and Ginchiyo.
Basically, just try this again in the story of Hideyoshi, and you should be able to get them, and transform tgem easily.