It does tell you the unit you need - you just have to click on the specific skill. For example Hinos Dragon Tiger Shot that needs any version of Kojiro.
Then again most Anime/Manga watchers will know what players are needed for what combo moves xD
Grats on Club Zsubasa, hope i get him soon as well.
Will do.
How do you see the explanation for each skill? Which menu option? I tried everywhere :(