Character mistake: During Fudomaru's story mode, the enemies in cutscenes have some problems with the word "ninja" used in plural or generic sense; the Twins say "Here comes ninja", and Ohga says "Is ninja never afraid to die?"
Character mistake: Shen Long's winquote against Hellstinger is "Hey kids! Your massage is a little rough." It's a single opponent, and calling him "kids" makes no sense. It's either a typo or a misplaced quote for the Platonic Twins character, which is two people in one avatar.
Other mistake: During Shaia's storyline (and in the movelist in case you defeat her) her sidekick is called Ballboy while the name is actually Ball Boy - same for her rival's Chrisboy/Chris Boy.
Other mistake: When you defeat BRIDER, you can acquire one of his special moves, which is called, of course, Double BLIDER Kick.
Other mistake: The credit roll lists as voice actress "Yuuko Nagasima"; her name can be written with one or two Us, but it is always "Nagashima" (including the anime).
Character mistake: When you defeat Karin, she says "I'm lost", instead of "I have lost."

Character mistake: Shen Long's winquote against Kyosuke; "Are you a really man?"

Other mistake: In the "How to Play" demo reel, we learn to "Move joystick back for DIFFENCE", which would be a pretty rad typo for "Defence."