|Spoiler Warning: Plot details, ending details, or both are in the text which follows.|
The Cruelest Thing is the forty-ninth episode of the anime.
After visiting, Petrov's apartment and finding notes from the kids claiming that the blonde girl did it and Grimmer is innocent, Tenma and Grimmer visit them in the orphanage. Grimmer tells Tenma that he has lost his emotions and that he often does not know how to react to situations and what feelings to show. Antonín meets with Tenma and Grimmer and tells them that they found the blonde girl but that Miloš has disappeared ever since.
In his apartment, Johan dressed as Anna, questions Miloš about his existence after he tells him that he is looking for his mother; he asks him if he is sure that someone wanted him. Tenma and Grimmer look for Johan and arrive to the apartment, but when they get there, Johan and Miloš have already left.
Grimmer tells Tenma the story about how, when his son died, his ex-wife asked him at the funeral why he was not crying, saying there was nothing in his heart and how then, after that, she left him. Tenma and Grimmer figure out that Miloš might have gone looking for his mother in the red light district at the Czech border. Tenma worries because he figures out that Johan will confront Miloš with the cruelest thing.
Johan, still disguised as Anna, takes Miloš to the red light district so he can look for his mother. Miloš walks throught the place thinking about what Johan said of his mother abandoning him. Miloš is witness to all kinds of depravation, including a German professor who has sex with a prostitue in the street and then gives Miloš 500 Czech crowns.
Traumatized by what he has experienced, Miloš walks to a bridge. Grimmer and Tenma find Miloš at the edge of the bridge while he is looking down, maybe thinking of jumping. Grimmer hugs Miloš and tells him that, while he does not have a mother, he was born because someone wanted him and Miloš hugs Grimmer back. Grimmer starts crying.
- Wolfgang Grimmer: "My emotions were stolen by Kinderheim 511."
- Johan Liebert: "Being born really isn't that uncommon... Almost everything in this world is meant to die. In this world, a life born is nothing more than an insignificant speck and shouldn't even be counted as existence. Death is natural."
- Kenzo Tenma: "You're crying,"