Yuki's Coldness is a one-shot written by Gamewizard2008, taking place in the Firstborn Saga. The one-shot is a first-person story told by Yuki Crystal, about how he was banished from the KND. Yuki had gained mysterious ice powers during a mission, when some unknown assailant blasted him with a gun. He accidentally froze Numbuh 363, and as a result, Numbuh 362 had him banished. Yuki's only friend, Jagar King, didn't stick up for him, making Yuki angry. Yuki went to go live in Zuzu's Valley of the North Pole, where Polaris allowed him to stay. Yuki decided he didn't need anyone, he was better off by himself. He did question, however, who it was that held the gun.
Yuki's Coldness was published on December 16, 2011.