The world's greatest criminal, pursued by the British authorities, who refers to himself as a consulting criminal. He skillfully uses bombs and assassins to escape situations, and his intellect is on par with Sherlock and Mycroft. He is a man who will do anything to get what he wants. His real name is James Moriarty, but he calls himself Jim, which is likely a nickname. As the arch-nemesis of Sherlock Holmes, who lives at 221B Baker Street, he mocks Sherlock's partner and friend John Watson by treating him like Sherlock's pet dog. He treats Sherlock as an equal and finds him entertaining. He has a relaxed and sly personality, often making jokes and appearing easygoing. However, when he gets angry, he does so properly, albeit quietly. He considers Sherlock's brother, Mycroft Holmes, a boring 'Iceman,' finding him too rigid and uninteresting. He is famous in the underworld but rarely reveals himself.

Moriarty's rival and a consulting detective. He lives at 221B Baker Street, sharing a flat with his partner and friend John Watson. He has little interest in money and is only concerned with cases that are interesting and stimulate his brain. He is an asexual who shows little interest in anyone, regardless of gender. A self-proclaimed high-functioning sociopath, he is actually just a brilliant individual who struggles with emotional expression and social skills. He is serious but shows a tiny bit of kindness only to his friend John. He smokes frequently and occasionally shoots at the wall when bored; his personality is not particularly pleasant.

Sherlock Holmes's partner and friend. A former army doctor, he now works as Sherlock's partner and a GP at a local clinic. He served as a military surgeon but was discharged after being shot in the right shoulder. He is straight and often frustrated by rumors that he and Sherlock are dating. Being a doctor, he is smarter than the average person, but he tends to be undervalued because those around him are exceptionally brilliant. He is kind but can be surprisingly firm.

Sherlock Holmes's older brother by seven years. A man holding a high position in the British government, he possesses significant power. He often cleans up after Sherlock's incidents. As his nickname 'Iceman' suggests, he is quite cold and analytical. He is slightly smarter and taller than Sherlock. Like his brother, he seems to have no interest in romance and is asexual. He enjoys tea and maintains a clean, sharp appearance. He is in direct opposition to Moriarty.