Burning Blood is all in Japanese with English subtitles. Actually, I didn’t even notice the subtitles while I was fighting until I watched someone else play. Luckily, the stuff said while you’re fighting isn’t terribly important. As far as I can tell, it is the same voices from the series. If it’s not, they did a good job impersonating the series. Your characters will say the same line for each move, so if you get by spamming a single button, get ready to hear the same lines over and over.
When you're playing a licensed game, you want the characters in the game to look like the characters that you are used to from whatever series the game is based on. In this case, the developers did a really good job of capturing the unique characters from the One Piece series. There are a whole lot of characters available, over 30 fighting and even more support characters, including obviously Luffy, Nami, and the rest of the Straw Hat Pirates, but also lesser known characters like Alvida and Cavendish. This means you will get to see a variety of people, from men in full battle armor to women in bikinis. Apparently, women can fight well in very little clothing.