Thunderbolt Fantasy: Seishi Ikken

Many years ago, humans waged a terrible war against the denizens of the Demon Realm. In the process, a series of special Shén Huì Mó Xiè ("Heavenly Instructor Magic Implements") weapons were forged to defeat the forces of the nether-realms. After the war, these sacred weapons were entrusted to the care of special guardians.The most powerful of these weapons, the Tiān Xíng Jiàn ("Sword of Divine Retribution"), was entrusted to the family of siblings Dān Héng and Dān Fěi. Now the leader of a rival clan, Miè Tiān Hái, will stop at nothing to possess this sword. While on the run from Miè Tiān Hái, Dān Héng and Dān Fěi encounter the mysterious stranger Lǐn Xuě Yā, who aids them in their quest.(Source: Crunchyroll)