Otaki is the chief inspector of the Osaka police district, and good friends with Heizo Hattori and Ginshiro Toyama. Otaki is also close friends with Heizo's son, Heiji, whom often calls Otaki when he needs to find information for an important case. Sometimes, Otaki even assists Heiji, and has a few times before lent a big helping hand in helping Heiji and Conan solve cases.