Question: how to unlock all characters in one piece burning blood?
Answer: The first thing that you need to do is to complete the game's Story Mode, Optional Missions, and Bonus Missions. This will essentially allow you to unlock the game's most of characters including Akainu, Kizaru, Aokiji, Whitebeard, Marco, Jozu, Buggy, Ivankov, Jimbei, Crocodile, Sengoku & Buggy.