The white-haired guy, aka Hans Lee, gives blood to Anzai in order to heal his wounds, but unfortunately, Anzai has no tolerance when consuming human blood and goes into a frenzy. Sawazaki and the cops go to Tsukasa’s place to see what had happened and they soon realize, by reading his temperature report, that Anzai is beyond control. When they go to the scene, they see Hans Lee trying to stop Anzai and the sniper ‘Zero Seven’ trying to kill them both. With the help of Hans, they manage to catch Anzai and sedate him but Zero Seven and her accomplice, Fifteen, escape. Two weeks pass and Tsukasa hasn’t heard from Anzai, which makes her go around the area that she last saw him, thinking that she might bump into him, but instead, she finds Hans there. They go around together, Hans explains her some things about oni and gives her hope that he can help Anzaiovercome his weaknesses. As they are on their way to find where Anzai is, a live weather report is taking place nearby where a slasher suddenly jumps in and cuts the forecaster in order to awake one oni that is nearby.
Monster (モンスター, Monsutā?) is the fourth episode of the Devils' Line anime series. It aired April 28, 2018.