A Re:Code, number unknown, under the command of "The Seeking One", whom he's fiercely loyal to. He seldom expresses emotions. His power is water form. He can freely manipulate the three states of water:solid ice,aqueous water and the gaseous vapour.
Among the Re:Code, he used to be very close to Kouji and Rui. However, unlike Kouji who still talks fondly of Rui, Yukihina has no qualms attacking and torturing her. He's also a personal opponent of Heike, whom he used to fight 3 days through until they both lost their powers in the past battle between the Re:Codes and the Code:Breakers. In the battle in Shibuya mansion, Yukihina faced Heike again. Their battle was postponed in favor of the fight between Ogami and "The Seeking One," and Yukihina witnessed "The Seeking One's" death with Kouji. Though he was unable to express any emotions and his mind just 'blanked out,' Rui told him it was because he respected "The Seeking One" the most, just like she did. Later, he reappears with Kouji to protect Ogami from the Code:Closer's attack, revealing it was a request from the late Code:Seeker, Ogami's brother. He then became a gym teacher at Ogami's school, thanks to Shibuya's manipulations.
The reason for his grudge towards Heike is because Heike made him an undead,thanks to which his wounds are immediately healed. It's also exposed that he's one of the First Generation Code:Breakers, which makes him, like Heike, around hundred years old. In his Lost Form, Yukihina turns into a woman.