Synopsis

Conan, along with his friends Agasa, Haibara, Ayumi, Mitsuhiko, and Genta, embarked on a camping trip. While there, exploring the grounds, they discovered a stone lantern nestled in a pond, its surface inscribed with cryptic markings. Presenting the lantern to Conan, he swiftly recognized the carvings as a complex code – a pathway to a significant diamond. However, the lantern concealed a further, darker secret: at the pond's depths lay a deceased person.