Ukitsu is a dark-skinned martial artist who's supposedly destined to kill Hakufu. She fights while wearing extremely heavy body weights and has an almost supernatural mastery of martial arts—she can pull from nearly every fighting style instinctively and with minimal chi use, which earned her the nickname "Genius Ukitsu." That lack of chi reliance actually made her a nightmare opponent for Hakufu, since Hakufu couldn't read her movements the usual way. Like Hakufu, Ukitsu genuinely loves fighting and craves stronger opponents, though she rarely found them before their encounter.
In the manga, Hakufu's dragon state overwhelms her badly. Koukin saves her life before it's too late, and she spirals into depression during recovery. She eventually gets a vision of Hakufu's dragon headed toward Nanyo, which seems to pull her back toward action.
The anime gives her way more screen time and a different trajectory. She shows up early saving an oblivious Hakufu from creeps at a karaoke bar, then works under her master Choukou to help Hakufu master the dragon—and keeps challenging her to fights, though Hakufu keeps passing out for unrelated reasons. When they finally do fight seriously, Hakufu manages to tame her dragon without seriously injuring Ukitsu. They end up becoming friends and agree to fight again on better terms, sealing the deal by removing their magatama.
In Dragon Destiny, she's actively trying to revive Hakufu. Turns out she's friends with Hakugen too. Choukou explains that since Ukitsu's literally fated to kill Hakufu, she's also the only one who can save her. The second season implies the first season's ending might not be canon—it would explain why Ukitsu's school didn't help during the war despite that alliance. She does successfully revive Hakufu, but dies in the process, sacrificing herself. She's buried near the waterfall where she trained.
Content compiled by AnimeList.moe from publicly available sources.