Kuina was Roronoa Zoro's childhood friend and training partner at their dojo. She's best known for being the one person Zoro could never beat in a sword fight—which, given what he'd go on to accomplish, says something about how skilled she was.
Kuina threw herself into kendo with relentless intensity, partly because she had something to prove. Her own father didn't believe a girl could ever reach the top of the discipline, and that kind of dismissal followed her everywhere. Even after she'd clearly become the strongest swordsperson in the dojo (with Zoro sitting at second-best), she still felt the weight of people's assumptions about her abilities.
One night, after overhearing her father's doubts, she sought out Zoro and challenged him to a proper duel with real swords. She won, as usual. But the victory felt hollow when she knew people were judging her based on her gender rather than her skill.
That's when she and Zoro made their promise: they'd both keep training until they became the greatest swordsmen in the world, and then they'd face off to settle who was strongest. It was the kind of ambitious, almost naive vow that only kids make—the kind that stays with you.
Kuina was also the original owner of Watto, the white sword that would eventually become one of Zoro's most iconic blades.
Content compiled by AnimeList.moe from publicly available sources.
