So this season's best series ends with an extended episode that wasn't quite the genius versus genius clash I was expecting, but was still an entertaining bit of crime solving.
The series as a whole has been an intelligent and fun piece of drama, with some smart solutions to the crimes (and some which were a bit unlikely). But the main strength of the show was the banter between the three main characters. Sato Koichi is great as the pompous commercial lawyer who gets carried away with being involved in real whodunnits, and he works well with Toda Erika who plays his eager yet slightly more sensible assistant. And Ohno Satoshi is fine in his role, although it doesn't ask him to really stretch himself as an actor.
Halfway through this drama's run, the BBC ran a story on the enduring appeal of "locked room" mysteries, and when they wrote that Japan is the new home of the locked room murder, I hoped that they'd mention this show, but no such luck. It does, however, suggest other classics of the same genre which I'll be investigating now that Kagi... is over.
It seems there's no end to this style of murder mystery, and with this series ending on an enigmatic note, I hope there'll be a second series or film sequel.