Unicorn Yato is the name of the Unicorn Saint living in the 18th Century. He was partner of Pegasus Tenma in the Sanctuary and he did not get on well with him. During the first mission in the manga he was defeated supposedly by Alone-Hades or one of his minions and he was thought to be dead by the other Saints.
Yet, he somehow survived and stumbled upon a dying Tenma. During his attempt to carry him away, a Lemurian girl called Yuzuriha appeared before them. Yato attacked her, mistaking her as an enemy. But after a conversation, he finds out that she is on the same side. Yuzurihaa then took both of them to Jamir, in Tibet, via teleportation. There, the Lemurian Master Hakurei repaired Yato's Cloth with the blood of Yuzuriha. After its repair, his Cloth looked like the one Pegasus Seiya used in the Poseidon Saga.
Yato claims that although he is not as strong or important as his partners, he considers fighting alongside them an honour. His only shown attack is the Unicorn Gallop (ユニコーンギャロップ ,Yunikōn Gyaroppu?) during which he performs a powerful kick. Yato seems to have a crush on Sasha as he always gets angry when Tenma mentions her, but the actual feelings he has have not yet been revealed in the story. He also sometimes risks his life to help Tenma; at the beginning of the series, just to prevent Sasha from being sad, but as the series progresses, he does it as Tenma's friend.