SHADOW SKILL: Kurudaryuu Kousatsuhou no Himitsu

Overview

The story takes place in warrior kingdom where a deadly martial art called Shadow Skill is practiced to defend the continued existence of the kingdom. Dreaming of becoming an invincible warrior one day, like the legendary warrior named Scar Face who has defeated 2,000 opponents, the boy named Gau Ban trains hard with his older adopted sister Elle who has mastered Shadow Skill. A deadly combat breaks out when a rogue pack of intruders suddenly assaults the castle to steal a box that contains a secret... (Source: Anime News Network)

Source: AniList