Teizokurei Monophobia

Teizokurei Monophobia summary:

Houdzuki Maika is a high school girl who, in a sense, is never alone. Her twin brother Maito, who could not survive birth, lives inside of her and shares her body. They switch between who gets to live each day and they share most of their memories. However, the only times they get to see and talk to each other is when they are both asleep, where they share the same dream. Perhaps as a result of this supernatural existence, they have the ability to see ghosts. These twins will surely face many mysterious events ahead!