You'll want to hang on to your Power of Love weapon/cheat for the first level to make this much easier, as well as playing on Average Joe difficulty. If you happen to break or drop your sword, load up in a shop to max your Heart and Guts to give yourself the best shot. While this is entirely possible on your first try, you can come back when your character is properly leveled up too.
In a multiplayer game you can cower and hold to constantly block while your co-op partner attacks if you'd like.
Power of Love sword unlocked at any stage
at the Title Screen