Meeting Conan/Shinichi, Ran, Kogoro, Agasa, and the Detective Boys is fun, despite the rather downer backdrop of the show’s initial premise.
Originally appearing in his own manga series before Detective Conan premiered, he just moseyed on over and made the jump to antagonizing Conan, Heiji, and the rest of the cast, on occasion.
Secondly, the episode throws a major curveball to Conan that hasn’t been previously seen in the series, though I can’t explain without spoilers.
When Conan and Ran get invited to Sonoko’s mountain villa for a weekend getaway, a murder obviously follows.