This case is easily a top 50, hell, a top 10 or higher case. It's soo good!
What I like the most about the Nagano police is their cases tend to have strong themes and the cases themselves are usually longer and more difficult/complex to solve.
Also, the Nagano police have some intelligent, component police members that Conan can easily swap ideas with without trying to dumb things down or give convoluted hints to get the message across.