Kairos is the Greek god of Time, specifically the god who governs special moments and opportunities. Due to his elder brother, Khronos, and the gods, he was trapped into a cycle of reincarnation, which he resents due to the constant suffering he endures as a human. His latest incarnation is the Hades Specter Mephistopheles Yōma, and he is the father of Pegasus Tenma.
After meeting with Tenma and Shion, Yoma activates his powers to show Shion and Tenma a vision of the future, showing Pegasus Seiya of the 20th century in a coma because of the cursed sword of Hades. Also it is revealed that his goal is not to serve Hades, but to change the future and allow him to start the war against the gods and his brother. This goal would require him to eliminate Shion so that the Pegasus Seiya in the 20th century will not fight against the gods in the 20th century .
Following the disclosure, Shion decides to confront Kairos and protects himself using Crystal Wall, however Yoma easily breaks through it with a burst of energy. Yoma attacks Shion using Marvelous Room, sending him to another dimension. To his surprise, the portal opens again with Gemini Aspros coming out of the portal carrying Libra Dohko and Shion, both unconscious. After a conversation with Tenma, he tells the Pegasus Saint to leave with Dokho and Shion so he can confront Yoma, to get revenge on the god for tainting his soul and for manipulating his life. Yoma attempts to once more attempt to kill Shion to change the future, but Aspros transports the dimension they are in to a dimension that is constantly changing at the speed of light, preventing Yoma from controlling time. Then, Aspros uses Galaxian Explosion to finish off Yoma. Believing that he defeated Yoma, he begins to leave the scene, but it's revealed that the Specter is still alive; uninjured by Aspros's technique, his Cloth starts to disintegrate, finally showing the Mephistopheles Surplice. After this, Yoma uses Bio Rewind on Aspros to devolve him to a pre-fetus stage, leaving only the Gemini Cloth behind. Believing Aspros died, Yoma bid farewell, muttering that he expected that the younger sibling to have better luck in the next reincarnation. However, Aspros reappears, wearing his own Surplice, explaining that the reason Bio Rewind had no effect on him was because Aspros was already dead and had returned as a Specter himself, meaning time manipulation on his body was useless as he is virtually immortal.
Once again, Aspros uses Galaxian Explosion on Yoma, but this only has the effect of revealing Yoma's true identity as the reincarnation of Kairos, the younger brother of Khronos, and a god of time and opportunity. Karios wants revenge on his older brother for having sealed him on Earth, forcing him to reincarnate among humans and feel an eternal cycle of pain and death. After Kairos's explanation, the spears used to decorate the clock behind the god become weapons used to prevent Aspros from moving when he prepared to to finish Aspros off, but the Gemini Cloth protects its wearer, with a stunned Kairos wondering if Deuteros was protecting his older brother. This allows Aspros to use Mao Genre Ken to trap Kairos in an illusion, where he babbles about his hatred of his brother, declares of war against his brother and the gods of Olympus, and his weakness as a god in his reincarnated mortal body.
Under the delusion Karios reveals that despite being a god, unlike Hades and Athena, he never chose to take on human flesh but was forced into it by Khronos, making his reincarnations incomplete and allowing Karios to be injured, to age, and even to experience death. Enraged, Kairos violently attacked Aspros, using his most powerful technique Marvelous Real, which began to compress Aspros body within a vortex with opposing rotations designed to rip a body apart. Luckily, using Next Dimension, Aspros teleports them both to the Path of the Gods, where Aspros explains that as Karios isn't fully reincarnated as a god, and doesn't possess a Kamui, he will be destroyed body and soul if he is pushed any inch closer into the dimension. Aspros then explains that he will seal Kairos's soul in the 108 beads Rosary, putting all the advantages in the Gemini Saint's hands; the only way for Karios to survive would be to at least have protection from a god to enter the dimension.
Aspros witnesses Youma's body disintegrate; Kairos/Yoma reflects on his love for Partita and how much he missed her. Aspros seals Karios inside the rosary made by Virgo Asmita. After Aspros himself disintegrates in front of Athena, Partita, now a Specter herself, appears before Tenma within the string of 108 beads. Watching the bead closely, Tenma observed that it contains the body of Yoma. There, Partita is shown holding her husband, torn and bleeding, but wearing a smile on his face, implying that Yoma was only really happy when he was with Partita. Finally it is revealed that the one holding the bead of the rosary was none other than Alone, revealing that he was using Kairos/Yoma all this time for his own objectives.
Attacks and Abilities
As the reincarnation of the god Kairos, like his older brother Khronos, he has power over time, ranging from being able to stop time and to see some future events, although he could not forsee his own demise. A reason for this anomaly could be that Kairos's power is limited due to seals placed on his body by Khronos.
- Marvelous Room (マーベラス ルーム): Creates a vortex/rift in space / time which leads the opponent to another dimension.
- Bio Rewind (リワインド バイオ): A time based technique that permits Yoma/Kairos to manipulate the opponent's biological clock. Can either rewind the opponent's biological clock to rejuvenate the opponent to the point of non-existance (pre-natal stage and beyond) or simply age them to death. So far, only Specters have been shown to be immune to this technique.
- Marvelous Real (リアル マーベラス): Generates a series of dark energy vortex which trap the opponent in a whirlpool, pulverising the opponent while it rotates in the inside of the vortex. Possibly most powerful technique that Yoma/Kairos possesses.