Heiji and Kazuha invite Conan, Kogoro, and Ran to tour the Exotic Quarter in Osaka. Kogoro is upset because of a tabloid article about Yoko Okino getting married, so he opts out of the tour to go drinking. As Kazuha and Ran are looking around the House of Fish they stumble upon the body of Keiko Uozumi, whom Heiji had met by chance while waiting for Conan and the Mouris to arrive by train. As the boys slowly investigate, another murder takes place, and the race is on to catch the culprit before they can kill again - and their next target might very well be Ran and Kuzuha!

[From Detective Conan World]