Kenji Fujikido, also known as Ninja Slayer, is the protagonist of the series 'Ninja Slayer'. He is a salaryman whose family was brutally murdered by ninjas, leading him to seek revenge. Possessed by the spirit of a vengeful ninja, Naraku, Fujikido transforms into Ninja Slayer, a vigilante dedicated to eliminating evil ninjas in the dystopian future of Neo-Saitama. Throughout the series, he battles various ninja clans and their leaders, uncovering deeper conspiracies and confronting his own inner demons, making him a complex character driven by vengeance and justice.