Kanon is a character with a substantial importance in the universe of Kurumada's manga, and therefore in its anime adaptation. He is directly responsible for triggering two main events : the conflict of the 12 temples by inciting Gemini Saga to succumb to his evil desires, and the resurrection of Poseidon, Emperor of the Seas. Also, Kanon is notable for redeeming himself after all his sins in the past and wreaking havoc as the Gemini Gold Saint in the army of Hades' 108 Specters.
Kanon is the younger twin brother of Gold Saint Gemini Saga, and later took up his position as a Gold Saint after Saga's death. Before finally embracing his destiny as the Gemini Saint, Kanon masqueraded as the Sea Dragon General of the North Atlantic, one of Poseidon's seven Sea Generals.
At first, Kanon was depicted as a treacherous man, always tempting his twin brother to use his status and power to advance his status of influence beyond that of a Gold Saint. He concluded that their amazing and powerful abilities were gifts from the Gods for them to take advantage of. Much to his dismay, his brother opposed this and caused his incarceration at Cape Sounion. After his redemption, however, Kanon becomes a much centered person, much like his brother.
Kanon was the one person responsible for Poseidon's awakening, although he kept Poseidon just half awakened so that he could pose as the true leader of the Marines as a Marine General and use Poseidon's army to achieve his desires. In order to do so, Kanon stole the scales of Sea Dragon and pretented to be the Sea Dragon General under Poseidon's order.
Even after joining forces with the Athena, Kanon retains his ruthless personality and harsh characteristics scolding Pegasus Seiya and Andromeda Shun that they should never hesitate to finish their enemies, because their hesitation is a weakness that their enemies would take advantage of. Even so, he quickly absorbs the honor of a Gold Saint.
Although Saga was extremely popular in the Sanctuary and practically worshipped by the surrounding villages as a healer and a protector, almost no one was aware that he had a younger twin brother, Kanon. Kanon is very different than his brother, for his ambitions and dreams of power corrupt his mind. Kanon accepts this as simply using their powers to further advance their status and there was no wrong doing in this. Kanon attempted to convince Saga to betray Athena whom had just been reborn after her two century absence in the Sanctuary, and that they could take over the Sanctuary to rule the world together. Kanon reminds Saga that the Gold Saint Aiolos is also favored to become the next Grand Pope of Sanctuary, and he should also be disposed of. Saga shocked by his twin's ambitions, deems Kanon a heretic. Saga confronted Kanon and easily subdued him before dragging him to the watery prison of Cape Sounion. Kanon prophecies that Saga's evil seeds would cause doubt in his mind and will haunt him for the rest of his life, he knows this because only a twin brother knows another twin brother. Kanon vows revenge against Athena and his older twin brother.
The prison of Cape Sounion was deemed mythical as it was impossible to escape from it, and the prisoners would end up drowned by the endless rising tides unless the Goddess Athena's will decided otherwise. Eventually, Kanon found a way to escape by breaking through the back wall of the grotto and entered a dark chamber containing the Trident of Poseidon with the seal of Athena on it. Easily breaking the seal and grabbing the Trident, Kanon was sucked into the depths by the resulting whirlpool and awoke in the Underwater Sanctuary of Atlantis, the realm of the Sea God Poseidon.
Upon exploring the temple of Poseidon, Kanon found a large room containing the seven Scales of the Marina Generals, the highest ranking protectors of Poseidon, as well as an urn sealed by Athena containing the vanquished and dormant soul of Poseidon. Upon breaking the seal, the spirit of Poseidon was released and inquired about the name of the person whom had just freed him. Concealing his true identity, Kanon looked about the room and his gaze fell upon the Scale of Sea Dragon, and claimed his name to be Sea Dragon.
Poseidon then proceeded to inform Kanon that it was too early for his awakening and that he would enter the body of his destined host (Julian Solo) and awaken in several years upon the latter's turning sixteen. In the mean time, Kanon would remain in the Underwater Sanctuary and ruled it in the name of Poseidon, commanding to the Marina armies and calling the other Generals to join him, including Siren Sorrento whom would later on, always nurse doubts about Kanon's true identity and motivations.
During the resulting war against Athena's Bronze Saints after Kanon manipulated Poseidon into kidnapping Athena and hold her prisoner in the Main Breadwinner pillar, Kanon faced Phoenix Ikki and the truth was revealed about his true ambitions to take over the world. Siren Sorrento then confronted Kanon and allowed Ikki to destroy the pillar Kanon was supposed to defend, thus allowing the Bronze Saints to enter the main temple of the Underwater Sanctuary and face Poseidon himself. In the ensuing battle, Kanon would realize his wrongdoings and would sacrifice himself by stepping in front of Athena to shield her from Poseidon's Trident (note that this sequence was modified in the anime adaptation having Seiya shielding Athena).
In the Hades arc, Kanon realized the error of his ways after his plot with Poseidon was foiled by Athena. He sought out the goddess and pledged his loyalty to her, where upon Athena gave Kanon the armor of his dead brother, allowing him to become the Gemini Gold Saint.
After that, Kanon kept watch over the Gemini Temple with Athena's permission. Because he was unable to physically protect the temple, Kanon used the talent for illusion that he shared with Saga to guard over the site. Ironically, it was Saga (along with former gold saints Capricorn Shura and Aquarius Camus) who Kanon had to do battle with in the temple. Using the same tricks Saga had perfected, Kanon created an illusion of himself wearing the Gold Cloth of Gemini to block Saga's passage. After having some troubles with the illusion, Saga sent an attack directly at the Pope's temple, almost hitting Kanon and ending his influence over the Gemini Temple.
In the Underworld, Kanon moved on his own, mentally controlling and killing the Specter Balrog Lune and challenging Rhadamanthys to a battle in which quickly overpowered him. Their fight, however, was interrupted by the arrival of some minor spectres, as well as bronze saints Seiya and Shun. Later on, Kanon found himself traveling with Shiryu and Hyoga as they sought out the palace of Hades. On the way, the group easily defeated many spectres, including the Deadly Beetle Stand of the Sky Ugly Star, and Lycaon Phlegyas of the Sky Guilt Star. Kanon and Rhadamanthys soon crossed paths once again, and Kanon instructed his two bronze saint companions to leave him as he battled the Wyvern Specter. The gold saint proved to be an adequate challenge for the Judge until Griffon Minos and Garuda Aiacos suddenly arrived on the scene. The two Judges expressed individual interest in battling the Gemini Gold Saint, and attacked him until Phoenix Ikki arrived on the scene.
Kanon and Rhadamanthys, both battle-worn, continued to fight to a stalemate. Eventually, 11 of the 12 gold cloths gathered together before the Wailing Wall. The Gemini Cloth was needed, and Kanon willfully returned it to his brother. Kanon, satisfied at the work he had accomplished, plunged onto the Wyvern with one last suicide technique, the "Galaxian Explosion" that propelled both men into the air.
In the ova 25, when the twelve Gold Saints join to destroy the Sighing Wall his soul briefly appears with the body of Gemini Saga. However, this is never explained.
Like his brother his most powerful attack is . When used at maximum power, the power of this move is said to be as powerful as the explosion of a star system or a galaxy, which is seen in the background whenever Kanon uses this technique. When it explodes the force of this technique can destroy souls whereas they have no physical body. and the more powerful allow Kanon to strike into the mind of his opponents. He can "brainwash" the opponent into doing his bidding and even make them go against their most precious assets. The effect of this technique can be undone only if the victim sees someone die in front of his own eyes. Although the Saint Seiya Episode G shows this technique as exclusive to the Popes of the Sanctuary, Kanon states he has this power. Using this technique he can also paralyze the targets nervous system, leaving him open to an attack. and allows his cosmo to bend the space and time itself to a different dimension, trapping his opponents inside. The technique not only sends physical bodies to a different dimension but also intangible beings such as soul. The second one holds connections with the Bermuda Triangle
As the SeaDragon Marina General, his Scales represent a sea dragon, mythical being of the seas. The temple Kanon guarded after recovering his status as Gold Saint was known both in manga and the anime adaptation as SouJiKyuu, the "Temple of the Twins".