Aka no Tachi

The manga centers on Akane, a girl who was unbeatable at kendo. She wanted nothing more than to fight her friend and rival Taki in an official match, and she finally got her wish in her last elementary school match, when they crossed swords for the first time. All that time, Akane thought she and Taki were even, but was surprised and disappointed when his skill surpassed hers. Bitter but unwilling to give up, Akane seeks to train even more and surpass Taki. But her unyielding spirit attracts another boy.

(Source: Anime News Network)

Note: Includes 1 extra chapter.