Kuina

Kuina (くいな) was the childhood friend of Roronoa Zoro. She was the daughter of the sword master of a dojo, the reason why Zoro developed the Santōryu technique, and why he treasures one of his swords, the Wadō Ichimonji, more than his others. In the English anime, the Wadō Ichimonji is just "Wado". When Zoro was young, he challenged every dojo he came across and claimed their signs (in Japan, the sign signifies the dojo is to be respected). When he came across Kuina and her family's dojo, he finally met his match.

Zoro fought Kuina regularly, but found that in 2001 fights he could never beat her. Kuina, after realizing that Zoro would soon pass her in skill and strength because she was a girl and he was a boy as as boys grow older they grow stronger then girls, so she became discouraged. At which Zoro told her that it was his goal to be as good as her, and together they promised that one of them would become the greatest swordsman in the world. However after she made a vow with Zoro, she fell down the stairs, while trying to get a sharpening block (no doubt to resharpen her katana after her and Zoro's duel) and died (in the English anime she was injured by the friends of a man she defeated, and could never fight again). Zoro asked her father for the honor of taking the Wadō Ichimonji with him, and with this Zoro promised to fulfil their shared dream of becoming the greatest swordsman to fruition in order to honor Kuina.

The Naval officer Tashigi bears a strong resemblance to Kuina (in appearance, personality, and sword style), to the point where it makes Zoro extremely uncomfortable around her. However, they are not believed to have any greater connection than that.

In the anime, she is voiced by Machiko Toyoshima in Japanese version, and by Priscilla Everett in the 4Kids English dub, who ironically also plays Tashigi in the dub.

She is a playable character in the U.S.-only video game, One Piece Grand Adventure. Surprisingly, Zoro says that she died