Tsukiumi

月海

She is Minato's fourth Sekirei, and her power is water (derived from her name "umi," which means the sea). She contacted him in a dream, stating that she would kill him, but when they finally met, she was persuaded to become his Sekirei. (chs. 22-23) She claims to be Minato's legal wife. Initially, she sought to become the strongest to prove that Ashikabi were unnecessary for victory, but later she confides in Miya that her sole goal is to grow stronger to protect her Ashikabi and live with him forever.
Tsukiumi is a Sekirei with a tsundere personality, the most aggressive member of Minato's party, and a very short temper; she rarely smiles. She was introduced as the first Sekirei who wanted to become the strongest without an Ashikabi's help. She even stated that she was willing to kill her future Ashikabi if she ever reacted to him/her, due to her hatred of Ashikabis[4]. She changed significantly after being winged by Minato and easily becomes jealous when Minato interacts with other women, owing to her feelings for her Ashikabi. She proclaimed herself Minato's legal wife, which sparked a rivalry with his other Sekirei, particularly Musubi, with whom she often competes for the title of 'Minato's legal wife'. Aside from this, she gets along well with Minato's other Sekirei.