Chika Mabuchi

Chika is practical and accustomed to dealing with tourists visiting Koumi Island. She operates her diving business professionally and is familiar with the local waters and the hazards associated with underwater activity.

Her role remains largely grounded in island life rather than the criminal schemes surrounding the treasure. She serves as one of the residents through whom the visiting cast experiences Koumi Island's diving culture.

Chika has no supernatural abilities. As the owner of a diving shop, she possesses practical knowledge of diving equipment and the local marine environment.

Her business supplies the equipment used by visitors entering the waters around Koumi Island, making proper handling and maintenance of diving gear part of her professional expertise.

Chika appears after Kogoro's group begins exploring the activities available on Koumi Island. Ran and Sonoko choose to go diving, bringing them into contact with Grotto and diving instructor Kimiko Yamaguchi.

The diving excursion becomes connected to the larger mystery when professional treasure hunters searching for Anne Bonny and Mary Read's legendary treasure operate in the same waters.

Chika remains a local supporting figure as Conan's investigation expands from an island vacation into a dangerous treasure hunt involving hidden ruins, manipulated diving equipment, and competing treasure seekers.

Kimiko Yamaguchi works as a diving instructor associated with Chika's diving business.

Ran Mouri and Sonoko Suzuki encounter Chika through their decision to dive while staying on Koumi Island.

Conan Edogawa becomes involved with the diving shop and its surroundings as he investigates the unusual incidents connected to the treasure hunters.