Johan is the main antagonist in the anime Monster. He looks like every normal boy does. With average height, well dressed and his short blonde hair makes us think that he's an ordinary youngster. No! Behind those looks hides a monster. Super intelligent, enraged by his past, his desire for murdering turns him into a beast. He manipulates and uses his victims. After that he takes their life away. He's killed mostly every foster family that he lived with. He has lost the human in him, doesn't know when to stop..or he doesn't want to?! He only respects his savior, Tenma. He constantly leaves traces and marks.
Johan has a twin sister with wchich he's separated. He strives the whole time to be together with her.