Insanely good story and deep philosophy. All characters is incredibly well written, and they've served their purpose in the story. Best anime I've ever seen.

The story revolves around Tenma and Johan philosophies that are against each others. Tenma believes that all life is equal and no one has the right to take life away from people, and this comes from his background as a doctor, who saves life no matter whose life it is. And Johan believes that no life is equal and the only thing that's equal is death. He has this belief because of his childhood memories and his character depicted as "monster". These two meet multiple times and every time they meet, Johan seems to provoke Tenma to break his rule of not killing people, thus proving his point. Tenma seemed to almost stray from his belief if not because of Anna, Johan's little sister who goes by the name "Nina Fortner". She has an incredibly amount of forgiveness, and willing to forgive everyone that has done her wrong like Mr. Muller, Peter Capek, and now his own brother, though it's not clear if she forgave Klaus Poppe for implanting a painful memory and starting a human experience on children.

The way they put the ending makes it open to interpretation. Audience could interpret whether Johan converted into good, or he wanted to start another serial killing event (I haven't read Another Monster Sequel so I just interpreted it based on what I've watched). For me personally it seems like neither, Johan was a serial killer but he knew what love is, shown by him loving his sister, and adopting her painful memories into his, so that he could keep his sister clean and pure. At the end of the story, I'm sure Johan is conflicted whether his mother loves him or just mistaken him for his sister, and he's searching for the answer to that one.

My favourite side character is Wolfgang Grimmer, a freelance Journalist who goes from place to place investigating child abuses (Klaus Poppe's program which he experienced in 511 Kinderheim). He's shown to be a kind man, who looks like you can beat him up in a second, but in reality just like Johan, he has a monster inside him that will show up whenever he's consumed by anger. The show "Magnificent Steiner" has a big impact on him as a person and basically sums up his character, as a person. He was unable to express emotions and didn't know how to feel when something happens, such as he didn't cry when his child passed away. Tenma helped him to search his emotions, and he was showing his emotion for the first time when he cried on a kid's suicide attempt due to Johan's manipulation. At the end of his life, he finally mourned for his child's death, and saying that emotions will never vanish, it's just wandering around in an unknown place. I really love him as a character and probably I could say the writing is equal to the main characters of the series.