Dancing on the Purple Rocks

 is one of the original non-canon short stories from Natsumi Mukai's +Anima manga.

Synopsis
Cooro patiently waits by a stall for some yakitori to be cooked, however some rival gang members get into a fight and one wearing a red bandana tumbles into the stall, knocking it and the yakitori to the ground. Angry over the ruined food, Cooro kicks the legs of a gang member wearing a blue bandana, causing him to fall down, and threatens the blues with his hatchet; they run away. Cooro checks with the stall owner before taking the spoiled food, however Nana Alba stops him from eating it. Impressed with Cooro's skills, Boss Frey approaches the two children and invites them to join his gang, which Cooro unhesitantly accepts because food was also offered. Husky and Senri watch them walk away.

Frey introduces Cooro and Nana to his gang's members. They comment that their numbers are now even again with Bruno's Gang, since they had too recruited two children. Frey leaves them at a table with plenty of food. Nana notices that all of the gang members are wearing red bandanas, to which another gang member explains that red is their gang's color, while blue is Bruno's Gang's. He goes on to explains about the gangs leaders' competition to become the new head boss of all local gangs, which involves finding the hidden treasure at the Purple Rocks. The mountain range is inhabited by dangerous creatures, so both gangs are on a recruitment drive. Cooro decides to stay until they find the treasure, but Nana isn't as pleased about the arrangement due to the gang members' inappropriate remarks about her.

Bruno hears the news that Frey has recruited two children and decides to make his play for the treasure. They ride out to the Purple Rocks at night, however Frey learns of their movements and gathers his gang to go after them. They find Bruno's Gang's horses, and start their own ascent up the mountain, however shortly come across a Red Rock-Dragon. In the commotion, Bruno's Gang ambush them; Senri slaughters the Red Rock-Dragon, while Husky fights Cooro. Nana hears another Red Rock-Dragon approaching and warns Cooro and Husky who narrowly evade it. Senri changes his arm into a bear's and attacks the dragon; Frey is surprised to see his claws. Cooro throws his hatchet into the dragon's eye; it staggers back, and with the handle attached to a rope, Cooro is sent high into the air. He stabilizes himself by sprouting his wings, and Frey is shocked to see another +Anima. Cooro lands on a rock, high up, which falls on the dragon, killing it.

From Cooro's vantage point he is able to see the treasure. Bruno and Frey race over to where Cooro saw it, beneath a rock on a cliff. As soon as they get close, Cooro lands causing the cliff to collapse and the treasure to fall. Cooro grabs it and falls into the lake below; he doesn't resurface so Husky goes in after him, using his fish gills and tail. After rescuing Cooro, they open the treasure to find some jewels. Nana and Senri soon find them, and explain that the gangs went back to town to prepare to retrieve the treasure. The children decide to head to the next town, however a tentacle comes out the lake and steals the treasure.