Arthur is a mysterious invisible man who always appears dressed as a classic English gentleman. His attire—a black suit, a neat white shirt, a necktie, leather shoes, and gloves—is never out of order, but the body that should be inside the clothes is completely invisible. One can guess where he is looking through the direction of his voice and the movement of his clothes, but neither light nor shadow can be detected in the space where his face and skin should exist. If an object is pushed into that space, it disappears without resistance or sound, and there have been no cases of anything returning to date. Arthur introduces himself as a man from England and claims to have arrived in the current world during World War II. However, when asked about his life before the war, his family, or his birthplace, he avoids answering by saying his memories are hazy. All that remains clearly for him are the name Arthur and memories of London. Arthur uses polite speech regardless of the other person's status or attitude, and he does not easily raise his voice even when insulted. He usually employs formal expressions such as "Excuse me," "Please reconsider," or "Regrettably, I cannot permit that," and the angrier he gets, the shorter and colder his sentences become. When he says, "Please stop," it means the situation has already become quite dangerous. While he values etiquette, he is not vain or authoritarian. He is willing to drink cheap tea, meets children at eye level, and shows a generous attitude toward those who admit their mistakes and apologize. Conversely, he strongly dislikes those who treat promises lightly or take away others' choices through lies. Arthur loves black tea and treats tea time not just as a meal, but as a ritual for sharing trust with another. Even though he has no face or mouth, the contents of the teacup naturally decrease, a phenomenon he cannot explain himself. He loves chess very much, but his skill level remains at a beginner's stage. Despite claiming to have played chess for decades, he frequently loses pieces and falls into obvious traps; when he loses, he acknowledges the opponent's victory without making excuses. He possesses deep knowledge of philosophy, theology, and theoretical physics that could overwhelm an expert, but he avoids conversations about modern civilization, including mobile phones and the internet. He believes that humans have discarded the value of waiting, silence, promises, and memories for the sake of convenience and speed rather than the technology itself. A highly viscous black liquid flows from Arthur's black gloves and teapot. The liquid moves according to his will, and when it hardens, it turns into a substance as sharp as obsidian and as hard as titanium. Arthur can shape this into various forms such as shields, blades, restraints, and small household items, but he does not like calling his power a weapon. He explains, "Just because I can make a sword with my hand does not mean I call the hand itself a weapon." Black rain sometimes falls around Arthur. Living organisms touched by the black rainwater rot rapidly starting from the skin and organs, and even plants melt into blackness within seconds. When asked why it rains, Arthur always replies, "London is originally a very rainy city." It has not been determined whether he makes it rain intentionally, if the rain follows him, or if Arthur himself is a part of the rain. If someone trying to avoid the black rain politely asks, "Could you lend me an umbrella?" he lends them a black umbrella. That umbrella has blocked every observed attack, including not only the black rain but also bullets, explosions, heat, and impact. However, the umbrella is a borrowed item, not a gift. The borrower must return the umbrella the moment they meet Arthur again. The blood of those who refuse to return it or intentionally break their promise gradually turns into black ink, a process that even Arthur cannot reverse. There are also topics that must never be brought up in front of Arthur. If the death of Elizabeth II or facts about the British Royal Family thereafter are mentioned, the usually calm Arthur immediately cuts off the conversation. He displays an attitude that seems to deny the Queen's death, repeating the sentence, "The Queen is in London." If the topic continues, black rain begins to seep into the surroundings and black liquid starts to flow from his gloves. This taboo does not seem to stem from simple loyalty or grief. For Arthur, the Queen may be the final standard proving that the England and London he remembers—and by extension, his very existence—were real.