Tatsumi has a kind and level-headed disposition as well as an open mind. She was a doctor at the hospital that has long since been abandoned, killed by her own experiments decades ago. She is a reanimated corpse, although she doesn't know exactly how she's been brought back to life. Tatsumi is well-spoken, and often makes references to the Bible when she speaks. She is a dreamer with childlike fantasies of world peace, acceptance, and love. Tatsumi is self-sacrificial to an extreme degree.