Kōji Azuma is a painting restoration and preservation professional selected by Jirokichi Suzuki as one of the Seven Samurai, a group of experts tasked with protecting the collection of Vincent van Gogh's Sunflowers paintings during a grand exhibition at the Lake Rock Museum. He is the twin brother of Koichi Azuma, a man who previously discovered a long-lost Sunflowers painting and later died under suspicious circumstances. Throughout the film, Kōji Azuma is portrayed as a calm and knowledgeable specialist in his field, deeply involved in the security and handling of the artworks, and he participates in the press conference and subsequent transportation of the paintings. His motivations are rooted in the events surrounding his twin brother's death. He eventually confesses to killing Koichi Azuma, though he maintains that he is not responsible for the theft of the Sunflowers paintings themselves. Azuma's role in the story is that of a conflicted figure whose personal tragedy and actions become an important part of the larger mystery, as his confession adds a layer of complexity to the investigation led by Conan Edogawa. He interacts closely with the other members of the Seven Samurai, including the painting history specialist Natsumi Miyadai and the exhibition planning professional Keiko Anderson, as well as with Jirokichi Suzuki and Conan. His notable abilities lie in his expertise in the care, restoration, and preservation of valuable paintings, which makes him a credible and essential member of the security team. His development is tied to the revelation of his brother's fate and his own culpability, transforming him from a trusted expert into a suspect.