US Normal = Jap Hard? Huh, didn't realize it heh.
For the first few missions in each part, everyone must survive.
For many missions, the enemy will simply sit there, waiting for you to get into range. So creep in toons with the opposing weapon just into their aggro range and BAM! easy xp + survival, yay!
And any enemy with a portrait who isn't the boss can be recruited. The key is figuring out who can talk to him/her without getting killed (you or the guy you're recruiting.)
Good Luck, Have Fun!
There is no such thing as a console war. This is the first step to game design.