Mariko is a nurse that assists Doctor Soga. She is usually seen as cold and emotionless, because she is no longer human. She's a reanimated Corpse. However, she happens to have a little more attitude and feeling then we are original exposed to.

Area D: Inou Ryouiki
The "prison survival action" story is set after the sudden emergence of special powers in certain pockets of humanity. To deal with these so-called "Altered," a mysterious remote island prison named "Area D" was built. (Source: MU)