William James Moriarty

The second son of the Earl of Moriarty. Entered university at 16 and became a mathematics professor at 21. While solving citizens' problems as a private consultant, he secretly leads a group as the "Crime Consultant," punishing the corrupt nobility. One of the Lords of Crime. Possesses a strong sense of self-sacrifice.

Addresses others as Surname-san. Uses polite, formal language. Calls Albert "Albert-niisan." Harbors intense feelings for Holmes, though they are officially friends.

Sherlock Holmes

A self-proclaimed "Consulting Detective" who speaks with a working-class accent. His deductive abilities are exceptional, earning William's respect. He is lazy and slovenly, often behind on rent and prioritizing his own interests. Despite this, he is surprisingly caring; Hudson notes he is "occasionally kind." Calls William "Liam." Harbors intense feelings for William. He is beginning to suspect the Moriartys' true identity but pretends not to notice since he lacks proof. Friends with William.

Usually addresses others without honorifics.

Louis James Moriarty

The third Moriarty son and William's biological younger brother. He suffered from a serious illness when first taken in but fully recovered after surgery. He helped his brothers take over the Moriarty house and, as an adult, manages the estate and household affairs in place of the eldest brother. He sustained a burn on his right cheek to "fake" a fire, which he now hides with his hair and glasses. One of the Lords of Crime. Speaks in very formal, respectful language.

He is willing to sacrifice himself for William. He adores William and deeply sympathizes with his ideology. Calls only Albert and William "Niisan."

Albert James Moriarty

The eldest Moriarty son. The heir to the noble family that took in William and Louis; he holds the rank of Earl. Possessing talent befitting an heir, he recognized William's genius—which rivaled his own—and simultaneously despaired of his parents and younger brother, who symbolized the "rotten nobility." He conspired with the two boys to eliminate his family and replace his biological brother with "William." One of the Lords of Crime.

He dotes on his younger brothers. Speaks in a gentlemanly tone. Deeply sympathizes with William's ideology.

John H. Watson

A gentle young man. Holmes's roommate, he has a reliable and serious personality. He occasionally quarrels with Holmes.

Addresses others as Surname-san. Unaware of the Moriartys' true identities.