Undine constantly releases her yoki to enhance her muscles, giving her monstrous strength and allowing for the use of two swords. Releasing yoki also gives Undine the bulky appearance she needed to get the Organization's approval in having two swords. Following Undine's death, Deneve took it upon herself to carry Undine's sword and practice using it to great effect. At present, her strength is enough to wield the two swords effectively without using yoki.