The story in short
Yone is Yasuo's older half-brother. They grew up together and sparred at Souma's school, with Yone forever trying to rein in his reckless brother.
When Souma was killed with the wind technique, Yone went after Yasuo and died in a duel with him. In the spirit realm an azakana demon attacked him, but Yone ran it through with its own sword and took its mask. Now he walks among the living again with two swords, hunting the azakana and searching for the one whose laughter he still hears.
