Lunar Legend Tsukihime

Shiki Toono was sent away from his family's household as a child after a life-threatening injury and was raised by a relative. Years later, he's ordered by his sister Akiha, the new head of the household, to move back in after the death of their father. Shiki harbors a secret: he sees lines on objects and can only stop seeing them with special glasses, and he has trouble remembering his life before the accident. His return to the household is marked by an unexpected encounter with Arcueid Brunstud, a woman he later agrees to be her bodyguard after a peculiar incident involving a knife.