Iwane: Sword of Serenity

Iwane Sakazaki has two childhood friends: Kinpei and Shinnosuke. The three are like brothers and train as swordsman in the same dojo. Kinpei has two sisters; Mao, who is married to Shinnosuke, and Nao who will marry Iwane. When a rumour reaches Shinnosuke that Mao is having an affair he flies into a jealous rage and kills her. Kinpei then kills Shinnosuke in retaliation for his sister. Iwane is ordered to kill his friend Kinpei and the two deadly swordsmen must meet in battle.