Koushakuka no S-Rank Jingi Tsukai no Kaiki

The Sacred Artifact, a weapon embodying one's soul. Born into the prestigious Catastrophe Duke family of holy knights, the protagonist Bell was the only one unable to manifest a Sacred Artifact and was exiled from his clan. However, Bell later inherited the legendary Sacred Artifact ‘Avalon’ and attained the strength of an S-rank holy knight. Returning to the ducal house to save his sister, Bell is killed by an unknown assailant. Yet, together with Avalon, he returns to his childhood. Now wielding the legendary Sacred Artifact, Bell's true life begins.

(Source: SORAJIMA, translated)