Boryoku no Umi is a Shinigami, a member of a race of powerful 'death gods/spirits' which, in the inukami setting, behave in a manner often hinting of insanity. A shinigami can do just about anything and will do anything - on a twisted whim. They delight in sowing death and destruction, with Boryoku no Umi being no exception. Boryoku no Umi first appears as the nemesis of the Shindō family, whose last member's guardian contracts Keita and Yoko to protect her. During his battle with Keita, he reveals that he has often granted the wishes of humans for the same price; by contract, he is allowed to murder the family members as they reach adulthood, one by one, until the whole family is dead. In the case of the Shindō family, Boryoku no Umi delighted in fighting any protectors they contracted with their own favored style of combat - and winning, killing all those who would not surrender. In addition to wearing a black shinigami robe, which deflects most ranged attacks, Boryoku no Umi is skilled in a vast array of martial arts and possesses powers of evil magic. Some of his favorite tricks are to awaken a person's deepest fears to paralyze them, or to evoke madness and terror by uttering a deafening shriek.