>>280260655
>>280260687
While it did start in the late 20s, Showa is typically colloquially used to refer to the late 50s to late 80s, which is the era is characterized by the post-war recovery economic boom. Hell, even if you talk about the era in the formal sense, that's a rare era to cover, and many go earlier. The closest to your description I could find is picrel, which is in the Taisho era.
In other words, please let me know where to find this Showa era murder mystery.