Fumimaru is an old ninja that works under Kōran Mori.
Fumimaru is a deceptive and cowardly ninja who prefers to attack his enemies mentally and emotionally, to the point that they'll kill themselves. He plays mind games with Recca by choosing to have either Yanagi or his adoptive father killed, by taking him hostage. After Kagerō rescued Shigeo and Recca escaped Nuibari, he took Yanagi hostage and threatened to kill her, unless Recca let him go. Recca, after having Yanagi close her eyes, used Shun En on him, forcing him to let Yanagi go. Surprisingly, he survived Shun En. After he tried to go after Yanagi again, Recca beat him up some and used Gen En, Rui gave him the choice of either a pit of flames or herself, he chose her, as she was a woman. She then burned him to death.
Fumimaru, while cowardly, is still rather clever and laid a number a trap all over the cave he resided in, as well as took Shigeo hostage. He carried with him a small knife.
He was rather tough, as he survived the flames of Setsuna.
He uses the madōgu Kagenui(影縫い, Shadow Sewing): Small throwing needles that can pin an opponent's shadow to the ground, preventing their movement. A person trapped can force himself or herself free, but will get injured in the process. Each needle has a small stone with the kanji for 'Sewing' (縫, Nui) written on it.
He and some of his subordinates have some madōgu that allow them to speak to each other over a distance.