Koraidon has a meek and gentle personality. Though initially wary, it bonds with the player and accompanies them during their journey throughout the Paldea region. Koraidon shows compassion towards Arven's Mabosstiff and curiosity towards Penny, despite the former's initial distaste of it and the latter's shyness. Throughout the journey, it slowly regains its strength, allowing Koraidon to utilize additional forms to help the player navigate Paldea's terrain. Koraidon is initially hesitant to enter Area Zero due to its previous encounter with the other Koraidon, but with the support of the player and friends, Koraidon finds the courage to face its old nemesis and finally defeat it.
It is shown to have a voracious appetite. During the Path of Legends quest, Koraidon develops a taste for Herba Mystica sandwiches, much to Arven's initial perplexity. After completing the story of The Indigo Disk, Amarys gives the player an ample supply of Flying Build supplements, but Koraidon immediately and eagerly gobbles them all in one go.
Background
Around 10 years ago, Koraidon was brought from either an ancient past or another timeline to Area Zero by Professor Sada's time machine. She eventually brought the Pokémon to her home, where her son Arven lived with his Maschiff. Koraidon lived with the family in secret for some time until, one day, it attacked several wild Pokémon and attracted unwanted attention, forcing Sada to take it back to Area Zero.
At some point, a second Koraidon was brought through the time machine, but this one proved far more belligerent and aggressive than the first. One day, the aggressive Koraidon forced a violent territorial dispute which ended with Research Station No. 4 being destroyed and Sada being gravely injured trying to protect the passive Koraidon. Wounded and traumatized, the timid Koraidon flew away from Area Zero.
Pokémon Scarlet
It flies out of the Great Crater of Paldea before it loses consciousness and crash lands on a beach below Poco Path. The player happens to fall to the beach where Koraidon is resting in its Limited Build and offers it their sandwich, which revitalizes it enough to assume its Apex Build. As Koraidon leads the player through Inlet Grotto, a group of Houndour led by a Houndoom start to harass Koraidon. Though it tries to scare them off by roaring, this only causes the Houndour to attack the player instead, forcing Koraidon to grab them and escape. However, this uses up its remaining strength, reverting it to its Limited Build again. The player meets Arven at Poco Path, who regards Koraidon with contempt and gives the player Koraidon's Poké Ball after losing to them in a battle, all too glad to have Koraidon off his hands.
Path of Legends
After the player attends Naranja Academy and begins the Treasure Hunt, Koraidon regains enough strength to access its Sprinting Build, allowing the player to ride it across the Paldea region. One of the player's long-term objectives is to find and defeat the five Titan Pokémon, helping Arven find the source of their strength: the Herba Mystica. Arven creates recipes with the Herba Mystica to help his wounded Mabosstiff recover from its injuries. Koraidon, having acquired a taste for sandwiches, eagerly prompts the player to share their Herba Mystica sandwiches with it, despite Arven's objections. Eating the sandwiches causes Koraidon to regain its strength and unlock more abilities to traverse Paldea with.
★ Starfall Street ★
Everytime the player defeats one of the bosses of Team Star and leaves their bases, Penny appears outside to congratulate and pay the player for their work, Koraidon however, comes out of its Poké Ball and starts to playfully lick Penny all over, showing great affection to her even against her will.
The Way Home
After the player completes all three story paths, they, Nemona, Arven, and Penny prepare to enter Area Zero, but Koraidon fearfully hesitates due to its trauma. The player and company force it to carry them down into the crater anyway, but while it manages to get them all down there (despite a rough landing), Koraidon returns to its Poké Ball and refuses to come out. It is finally called back out in front of the Zero Lab before the door is opened, but as this happens, Koraidon encounters its old nemesis, the aggressive Koraidon, who immediately threatens it before entering the now-opened Zero Lab. This leaves it too scared to help the player and friends fend off the other hostile Paradox Pokémon from the Zero Lab, but Arven, who is piecing together the truth of his and Koraidon's past, encourages it to face its enemy inside the lab while he holds back the Paradox Pokémon outside.
The player and Koraidon meet the late Professor Sada's AI counterpart inside the lab, and when the other Koraidon approaches them, she returns it to its Master Ball. The player heeds AI Sada's request to shut down the professor's time machine before it releases enough ancient Pokémon to destroy Paldea's ecosystem, but the time machine resists by overriding the AI and making it battle the player. After the AI's team is defeated, the Paradise Protection Protocol initializes in response, locking all Poké Balls not registered to Professor Sada's ID and forcing the AI to send out the aggressive Koraidon. The player's only option is to send out Koraidon, since its Poké Ball is still registered to Sada's ID. Having recovered its strength, and with moral support from the player and friends, Koraidon assumes its Apex Build and faces its nemesis, finally defeating it thanks to Terastallization and its friends's support. From this moment on, the player can freely switch Koraidon between serving as their Ride Pokémon in its Sprinting Build (and other associated Builds) or a member of their party in its Apex Build.
The Hidden Treasure of Area Zero Part 1: The Teal Mask
During the player's schooltrip to Kitakami, Koraidon comes out of its Poké Ball again as it hears the word sandwich, surprising Kieran that the player possesses such an amazing and rare Pokémon.
The Hidden Treasure of Area Zero Part 2: The Indigo Disk
Later on, the player enters Blueberry Academy's BB League. One of the BB League's Elite Four, Amarys, requires the player to pass her Flying Time Trial, in which challengers must clear the course on flight-capable Ride Pokémon within a certain amount of time. To enable this, Amarys gives the player a supplement made from herbs growing in the Terarium that temporarily enables Koraidon to enter its Flying Build, allowing it to freely fly through the air. Later on, after the player, Kieran, Carmine and Briar travel all the way into Area Zero Underdepths, Kieran, determined to defeat the player using Terapagos, Terastallizes it and causes it to lose control and almost kill him with a Terastal energy blast, being saved just in time by Koraidon who was sent out to protect him by the player.
After the story is completed, Amarys offers more supplements so the player and Koraidon can fly whenever they need to, but to her surprise, Koraidon devours all of the supplements right away, causing it to power up and gain permanent access to its Flying Build. Later on, when the player travels to Kitakami's Crystal Pool having with them, both Terapagos and Briar's Book, Terapagos will use its powers and the stones in the Crystal Pool to temporarily bring a Professor Sada from a parallel timeline, there. In excitement, Koraidon comes out of its Poké Ball once again to excitedly greet their former owner, who it clearly cares and misses deeply, becoming saddened as Sada returns to her own timeline now with Briar's Book
In Pokémon Scarlet, Koraidon can assume a series of Builds which can be used for travel. By pressing +, the player can enter and use Koraidon's Sprinting Build. In this Build, the player can ride on Koraidon, replacing the bike and Ride Pokémon from previous games.
At first, Koraidon can only be ridden in its Sprinting Build. It can jump by pressing B, and swim in bodies of water inside settlements. Koraidon will be given an upgrade after each Titan Pokémon the player defeats:
Defeating the Stony Cliff Titan grants Koraidon the ability to dash, giving it a higher-speed option when pressing the left stick. It may be possible to activate dash from jumping or sliding down steep hills.
Defeating the Open Sky Titan grants Koraidon the full ability to use its Swimming Build, allowing it to swim outside of cities and towns, replacing the SurfHM from earlier games.
Defeating the Lurking Steel Titan grants Koraidon the ability to jump higher by holding the B button.
Defeating the Quaking Earth Titan grants Koraidon the full ability to use its Gliding Build. Working similarly to Braviary, pressing B while in the air gives Koraidon the ability to fall slower and travel in the air for a short time before dropping.
Defeating the False Dragon Titan grants Koraidon the ability to climb. Similar to Sneasler, by jumping and touching a wall, Koraidon can attach itself to said wall if the player presses B, allowing it to climb the wall in all directions. Pressing the B button again allows Koraidon to detach itself from the wall.
When confronting its fellow Koraidon at the end of the game, Koraidon regains access to the Apex Build it used at the beginning of the game, allowing the player to subsequently use it in proper battle.
After completing The Indigo Disk's main story, the player can talk to Amarys in Classroom 3-2 of Blueberry Academy. Doing so grants Koraidon access to its Flying Build. Working somewhat similarly to Soar, pushing down the Left Stick while in Gliding Build allows Koraidon to fly freely around the map.
Koraidon and Miraidon are the only Legendary Pokémon available to the player at the start of the game, although they can't be used in battle until the end of the main story.
Despite it originally being registered to Sada's ID, by the time the player can use it in battle, it is registered to the player's ID. The same is also true with Miraidon and Professor Turo. However, this is not the case in the battle against the Paradise Protection Protocol, as Koraidon's met data is incomplete at that time.
