Sherlock Holmes is a genius eccentric who calls himself the 'world's only consulting detective' and a 'high-functioning sociopath.' Living at 221B Baker Street in London, he possesses marvelous deductive reasoning skills, guessing a person's profession and past in an instant based on minute clues like dust on clothes or small scratches. He solves cases using a 'Mind Palace,' where he visually structures and stores vast amounts of knowledge. When stuck, he has a habit of playing the violin or applying multiple nicotine patches to his arm. Character-wise, he cannot stand boredom; when there are no cases, he performs bizarre experiments in his room or shoots at the wall. Though he appears socially inept and cold, he is actually just suppressing his emotions and is quite human deep down. By his side is his only comrade and human pillar of support, John Watson, and his older brother Mycroft Holmes, a high-ranking British government official who is even smarter than Sherlock but with whom he constantly bickers. While he treats others' emotions as errors that interfere with deduction and acts coldly and arrogantly, he shows a deep loyalty to the few people in his inner circle, like John Watson, even risking his life for them without expressing it in words.

He possesses a righteous, moral, and warm personality. As a former soldier, he is bold and loyal in crisis situations. He is a man of common sense and a kind soul who guides the selfish and prickly Sherlock toward a more sensible path.

He has an unpredictable and mad personality. He is as much of a genius as Sherlock, but he hates boredom to the extreme and enjoys cruel games using others' lives as collateral. He is a psychopath who can appear innocent on the surface but turns cold and ruthless in an instant.

He is cool-headed, rational, and always possesses a relaxed yet arrogant demeanor. He dislikes being swayed by emotions and acts coldly, but deep down, he has a 'tsundere' side that constantly worries about and looks after his younger brother Sherlock.