Zenji is one of the main antagonists in the story. His origins or connection with the Yamamoto Clan is unknown, nor is it how he lived for generations and didn't age. Legend says that he's the descendant of the most powerful demonic spirit named Enenera. Who, is also the main reason the clan was resurrection to dark humanoid revenant. Zenji is shown to be calm and collected but also ruthless and deadly. He was responsible for the Mark brother's parents' disappearance and other Rajiu family members. Without the proper background or reason why he waited for millennia and targeted the Raiju Clan, it was unclear what his true motives were. Regardless, he's a threat and a force to be reckoned with.