If you're a "Shōwa person" like me (and that could mean either that you were born in the Shōwa era, or that you feel a particular affinity to it - or both, as is my case, LOL), there's a high chance you too will like this "Kekkon Annai Mystery".
Right from the first minutes of it, thanks to the music, the clothes, and most of all to that dark computer screen with the bright green text (which all help bring us older viewers back to the '80s quicker than Doc Brown's DeLorean would ^_^), you get that unmistakeable "end of Shōwa" flavor, and that's already half of the movie's charm.
The rest is done by the exquisite directing (I guess the director had studied proficiently the Italian Golden Age Thriller Masters, like Lucio Fulci and the first Dario Argento - and indeed, the first scene reminds a bit the beginning of "Profondo Rosso", while several others will make the more knowledgeable among you reminisce about movies like "Sette Note in Nero"...and why not, some takes were done in the style of Hitchcock's classics too!), by the score, the editing, and by the general, intriguing atmosphere. The cast did well, with a particular praise to Nagayama Aiko who really stole the show here!
The fact that, being only 90' long, the movie felt a bit rushed, and that the mystery's solution imho felt a bit bland, prevented me from giving this a "perfect 10". It's still a solid "9" for this lovely "oldie but goldie" though! ^___-