Maria Asagi
Maria was Brandon's sweetheart when they were young. She lived with her adoptive father Chester, a member of Millennion, who raised her from infancy after finding her while working a job for the group. After Chester was killed, she moved in with Big Daddy at his villa, eventually growing close to him after Brandon rejected her, on the grounds that he had sinned too greatly during his profession as an assassin. Spoiler She eventually married Big Daddy and gave birth to his daughter, Mika. Maria was later killed by Harry MacDowell, in his attempt to discontinue the line of Big Daddy's descendants. (From Wikipedia) Spoiler A flashback in the game reveals a clearer reason why Maria's daughter is someone important to Grave--during the time when Brandon was still human, a pregnant Maria asked him to make a promise: to always look after and protect her child should something happen to Maria or Big Daddy. This promise is one of the few memories Grave still retains of his previous life.