The Witch's House: The Diary of Ellen Vol. 1 (manga)

"I know all too well...the beginning of that diary I never wrote-"Ellen, who has been plagued by sickness her whole life, heavily relies on her mother's care and love. When the bond between them decays in a horrific turn of events, Ellen despairs that she'll never get the love she so desperately craves and thinks she's done for-that is, until she crosses paths with a mysterious black cat. The cat offers her powers and a house to live in, which seems to change Ellen's life for the better. But the new witch soon discovers the gruesome secrets within this ever-changing house...