Like Seiya, the anime protagonist, Koga is rude, hotheaded, and reckless but he is brave and kind Saint.
Arrives in Earth
Kōga is not a true human being. He is hosted by the dark god, Abzu, and because this, he uses the darkness element. So, Kōga is the mortal body of Abzu, that would born in the Earth as a baby. But, after Medea invokes a meteor (in the first war against Mars) to bring Kōga to the Earth, Athena removes the Abzu darkness of he, and give her light to the baby, and because this, Abzu don't possessKōga (only darkness being can invoke Abzu)..
Second War against Mars
In the Sanctuary, the baby Kōga witnesses Mars came back to kill Athena. Mars hurts Athena with darkness hurt, and Seiya vanishes after almost destroy Mars body.
But, Kōga was only a bit of time a good darkness hero, because hedoesn't use the darkness to save his friends, and when uses, he gets crazy and amoral; only in the final of Mars arc, in the fight against Amor, Kōga uses his darkness to free his friends, but these darkness, although used for a good goal, have an evil origin.
After Mars hurt Saori with the darkness (can't fight against Mars and need accept his rule because this in that time) hurt and Ionia rule in Palaestra with Mars influence, Saori hid in a small island of Italy with Tatsumi, Kōga and Shaina. Probably, how Palaestra was dominated by Mars, Saori asks to Shaina trains Kōga in that island (because if he went to Palaestra, will become a Mars servant) too, like the original series, made an army of servants to retake the role of the Sanctuary.
Kōga never knew about Seiya and the divine nature of Saori, and because this, never trust in Shaina words about the saints must protect Athena and Seiya dead to save him (Kōga thinks Athena only exist in the Greek religion). So, Kōga don't wish to become a saint.
Third war againt Mars
Kidnap of Saori
Kōga discovers Saori is Athena, and consequently, that Athena really exist. Mars arrives regenerate in the island and kidnaps Saori. Hedoesn't know what happened to Saori, but, he knows about a thing: he must save herself.
Sōma and Palaestra
Kōga begin a journey to save Saori, and meet Sōma, a fire element saint, and he says (almost no one saint knows Saori is Athena) Athena is well, in her Sanctuary. Sōma guides Kōga to Palaestra, a school where Sōma studies (are not explained why Sōma is out of the school) where Athena must be.
In Palaestra, Kōga meet new friends (Yuna, Ichi, Ryuho) and rivals (Eden, Spear, Rudolph and Gray). There, he completes his training and domains his element (how he doesn't know about the history of Seiya and Saori, he thinks he element is the light). He meetsGeorges (teacher), the vice-principal (name is unknown, and he is severe with Kōga) and Ionia (the principal, and was friendly with Kōga).
Kōga join in a tournament between students of Pallaestra, because who win, can see Athena. During the tournament, Kōga win a fight, but after tries find Athena in her room, discovers she is not Saori; she is Aria. The Kouga's light does Aria recover his true conscience, and Ionia show his badness, and kidnaps Aria.
Kōga was arrested, and in the prison, meets Haruto, and with him, gets away from that prison with help of Kōga's light. Kōga, Haruto, Yuna, Ryuho and Sōma, leaves Palaestra after Geki help, and now, must save the students and teachers of there.
In the Babel Tower, Kōga rescue Aria, with his comrades help. Now, they must protect Aria, because Mars ordered evilly and mistaken saints to kidnaps Aria again.
Aria must use her power to destroy the 5 ruins of Mars, to save the cities around they and save Palaestra (because these ruins absorbs cosmoenergy of the things around and give to Babel Tower, and this tower send the energy to Mars). Kōga with Aria, fights against ruins protector.
Eden and Hyoga
Eden reveals to Kōga and Yuna, he is a Mars servant. Kōga tries defeat Eden, but him show his power, and injures Kōga and kidnapsAria, and takes her to Mars Castle. Because his failure, Yuna gets angry; she shows a place where she goes when she gets sad, and there, finds Hyoga (Kōga didn't know Hyoga, because he did not know the history) and he has a conversation with him, and after, Kōga decides rescue Aria.
Kōga arrives at the castle to save Aria; there, the comrades of Kōga fights against silver saints to allow Kōga saves Aria, but she was no longer there. She went to Thunder Ruin with Eden.
Thunder and Dark Ruin
Kōga arrives in the Thunder Ruin, and after the battle against Eden, Kōga gets angry and invokes his darkness Cosmo, and only Aria hasthe power to bring him to normal person.
After Aria's became Athena, Mars kills her and steals his stuff. Aria's uses her Cosmo to guide Kōga to Babel Tower, where are the New 12 Temples.
After Kiki, don't show his goodness to Kōga, he tries to fight againsthim, but Kiki defeats him and tell he is a good guy. He fixes Kōga's cloth first, and Kōga don't wait and goes alone to Taurus Temple, while the cloth of his friends are fixed.
Kōga fights against Harbinger, and he breaks various Kōga's bones and lets him unconscious. Yuna and the others fight against Harbinger, but he teleports them, and Kōga fights alone against him. Harbinger after seeing the determination of Kōga, allows him to pass, to see how strong he can be.
Kōga helps Ryuho in the fight against Paradox, and after, leaves the temple, leaving Ryuho fight against her.
Cancer Temple and Possession
Kōga was send to Yomotsu and tries help Yuna, but he was possessed by darkness of Abzu (he was not possessed by abuse, but, his darkness made Kōga a bad guy) and with no Aria, Yuna saves Kōga. Yuma defeats Schiller and after, they go to the next temple.
Kōga almost was defeated by Fudou (he neither hurts Fudou, nor didhe gets up).
Kōga was defeated by Tokisada, and Gembu saves him and teleport Tokisada to his temple to him don't kill Kōga and his comrades. Kōga see the battle between Tokisada and Genbu, and after, goes to Scorpio Temple.
After Sonia fights against Kōga and Yuna, Sōma fights alone against her, and Kōga and Yuna goes to Saggitarius house, and in the road to there, see snow falling; it's Sōma, burning his seventh sense.
Kōga see there, the Aiolos testament, preserved even with the Sanctuary destruction.
He finds Ionia there, and resist the Ionia body-control attack (Ionia try to induce Kōga to attack Yuna, but he resists), and defeats Ionia with his seventh sense..
He meets Amor, a saint that invokes the 4 Four Heavenly Kings of Mars, and hold Kouga in a bar person, that only can break, with a darkness Cosmo. So, Amor wants arouses Kōga darkness Cosmo to invoke Abzu and he made a dark world to Medea. Kōga, to help his friends against the enemy, uses his darkness to escape of theperson, but he gets control over it, and defeats Bacchus. But, Amor tries to bring Kōga to the dark side with his own darkness, and Yuna uses his friendship to bring Kōga back to the normal.
Kōga leaves Amor with Yuna in Pisces temple, and arrives in Mars garden, where fights against him, and later, he fights with Eden help. Kōga and Eden defeat Mars, but he dies before he can save the Earth of the consequences of his scheme, and now, the planet Mars threatens life on earth. So, Kōga must go to Mars, and recover the staff of Aria and save Saori.
In Mars, Amor uses the Mars darkness to defeat Kōga and give it to him. But, Kōga even having a divine darkness power, don't invokeAbzu. Medea wants Amor know about their scheme (where he is dead and only she and Eden rule in the Earth) to he tries kill Kōga and provokes him to Abzu finally awake.
Abzu possess Kōga after he sees Saori, and Seiya arrives at the place, and again, with Yuna's help, remove Abzu from Kōga body. He is the once person that can access Abzu darkness, and with Sagittarius cloth, goes to another dimension in this darkness, where Saori was imprisoned.
He after a battle, saves Saori and defeats Abzu. He almost dies, but Aria's soul saves him.
Aria and Kōga
Kōga and Aria in the history were good friends, but don't be a couple. Aria and Kōga have the same origins, so, the two boys of the same elements in that time, have a strong link, and because that, was good friends and close people.
War Againt Pallas
Return to Island
Kōga leave the saint office after the break of his cloth, and all Athena's enemies were killed; so, Kōga come back to his island, to have a life like before the Mars battle; a new rival, Subaru, appears to defeat Kōga, to become a god, because Kōga killed a god (Abzu). But, the pallasites, the last Athena enemies, come back to the Earth and Tarvos tries to kill Kōga. So, Kōga uses his cloth, and how it was bathed in divine blood along the History, it's self-regenerates and now, Kōga can to fight.
Kōga with Subaru goes to Greece, Jamir, China and Japan, to try to convince Sōma, Yuna, Ryuho and Haruto to fight against Pallas.
To be added.
Kouga gets the Omega Cosmo
To be added.
After Saturn defeats, Kōga comes to travel the world in a journey, and leaves his friends.
Kouga was a dark saint, using Saori's light. After defeating of Abzu, he doesn't possess no element, but uses light attacks (and his element after Abzu leaves his body is the light, because only left the light of Saori in his body after the Darkness of Abzu escapes from his body [because Abzu bring all his darkness with him and made another dimension to it]).
Kouga as a saint, have a strong Cosmo, can use a hard armor (cloth) in his body, and can do high speed attacks, a cosmicexplosion, and a cosmo power ray; he has the Omega cosmo in the end of the series.. But, he has special techniques:
- Pegasus Ryu Sei Ken: Kouga fires 100 punches by second in the enemy, and these punches become energy balls (meteors).
- Pegasus Senkouken: Kouga launches a light sphere in the enemy.
- Pegasus Sui Sei Ken: Kouga mixes his meteors in a big sphere (comet), unlike the Pegasus Senkouken, that is only a light ball with no meteors mixed in it.
- Pegasus Rolling Crash: Kouga grabs enemies backwards, and takes him to the top and falls on the ground.
Relatioship with his friends
- Eden: Is the Kōga rival, but Kōga like him and after a long time, understand his personality.
- Yuna: After Aria's death, Yuna always help Kōga in hard times. Yuna admires Kōga, and according she, he is a jerk, and jerks never gives up.
- Sōma: Is the best friend of Kōga and as jerk as him.
- Ryuho: Is only a friend of Kōga.
- Haruto: Is only a friend of Kōga.
- Subaru: Is only a friend of Kōga.
- Tatsumi: Kōga thinks he is krusty.
- Shaina: Kōga has value on Shaina, and he is a
- Saori: Kōga have a crush on her, and want protect her.
- Seiya: Kōga is his love rival (although Seiya created Kōga like his son, but Kōga don't remember this), because Saori and him are the best friends and probably boyfriends.