Chief of the 2nd Division, 2nd Section of the Metropolitan Police Department. Rank: Assistant Inspector. She became acquainted with Guest when she went to the Paris Police Prefecture for training. She suspects the Englishman who met Guest resembles a British intelligence agent who once targeted her notebook, and she keeps a watchful eye while issuing warnings.

33 years old. He introduces himself to Guest as Jian Verdi, acting as a museum curator from England to reclaim King Richard's Ruby, which Guest's father donated to the museum. His real name is Gian Cabrini. His physical capabilities far surpass Steve's. Four years ago, he was solving mysteries with a Japanese woman, but she (Yumi Sawamura) was shot in the left shoulder and fell from a bridge in Naples, Italy. That woman remains his trauma. If he ever encountered her (Yumi Sawamura) again, he would likely keep her by his side forever (he has some overprotective yandere tendencies...)

28 years old. An agent of British intelligence. He provides support for Jian but grimaces upon learning that Suzuka Narumi is handling security. He feels uneasy about how Utsumi seems to anticipate their every move.

31 years old. Chief of the 2nd Division, 3rd Section of the Metropolitan Police Department. He appears before Suzuka Narumi and Guest due to a heist notice from the phantom thief Cat targeting the ruby (which is actually a fake notice created by Steve). He acts on the prediction that the two (Jian and Steve) are the thieves. He is the finest marksman in the 2nd Division.

27 years old. A member of the Metropolitan Police Records Department. She informs Chief Utsumi of the 3rd Section that Jian and Steve are the ones targeting King Richard's Ruby. When she was 23 and solving mysteries with Jian, she was shot in the left shoulder by 'The Professor' on a bridge in Naples, Italy, and fell into the river. The one who saved her was the phantom thief Lupin, who also paid for the surgery to remove the bullet.

A butler serving Quide. 69 years old. He moved from France to Japan with Quide's mother. His name is Marshall Moret. He is strict with the British. He is very polite toward Yumi Sawamura because Quide's father had a mentor-student relationship with Keiichi Kunimi, and Keiichi's friend is Yumi's father.

Arsène Lupin Lidford (46 years old). Half-British, half-French. He spoke to Utsumi in French (Utsumi-kun also conversed in French... though they started speaking Japanese to each other afterward). He does not seem to welcome the return of King Richard's Ruby to England... His true identity is a member of British intelligence, codenamed Gareth. Feeling something is off about the nature of Steve's mission, he shows a cooperative stance toward Utsumi and his team. Moret evaluates him as someone whose recommendation by the hardliners of the Lupin clan is understandable.

Victoire Leroux (65 years old). She began serving Arsène's mother at the age of 19 and is now the maid assisting Arsène. A Frenchwoman. She was an acquaintance of the father of Utsumi's childhood friend, and having heard stories of Utsumi from him, she holds him in very high regard. Regarding the British, she respects Arsène's father but shows no respect to the British who come to steal the ruby.