I finished 香水心中!
The first time I tried reading it right after 殺人鬼 I definitely made the mistake of thinking about it like “I’ll just blitz through these two stories and finishing a book will be fun!” instead of like, “reading these two Yokomizo stories will be fun!” and due to taking too long a break between chapters and not reading carefully enough, by the point where Kindaichi’s talking to the driver about various characters and circumstances I had completely lost track of the exact details of what they were talking about.
I think the biggest thing that did me in was Miyoko being introduced with her relation to the situation not being explained, as then when I picked the book up again I remembered strongly the detailed family backstory but completely forgot that she was introduced separately to all that and so assumed she must be one of the female characters I remembered learning about and so was just confused when those ones showed up separately… 
Anyway, I stopped reading and only came back to it now which was the right choice I’d say.
To keep that from happening again, this time I took very crude notes - not bothering at all to check if my name reading guesses or anything like that was correct but just as a consistent personal reference to have on hand as I went along.
Might as well share them!
香水心中 Notes
NOTE: this piece has setup spoilers incl. things that happen and details revealed midway through the story, but nothing that spoils the mystery
NOTE: this is an awful timetable that includes crucial mystery details revealed late in the story but no solution spoilers
I actually enjoyed that process! I’m sure Eight Graves probably has a very helpful wikipedia page like past novels (and like, as it turns out, 香水心中, I guess I just assumed it wouldn’t?) but I might consider just taking notes for that too since it was pretty fun and did help me visualize what happened at different points and remember names better.
… It did make the ending feel especially abrupt though. I don’t really like how this one pretty much just skips right past Kindaichi deducing anything? It’s not completely out of character with other Yokomizo stuff we read, but maybe since I had relatively elaborate notes this time ready to see how it all connects, it was particularly a bummer to have it then cut directly to like, the culprit’s letterhead as he then just says what happened, with just sort of an implication that Kindaichi could/would have figured it all out, or did off screen or something.
I like a lot of the elements, like the perfume dynasty with the completely carved away gap generation, the evocativeness of the phrase “香水心中” and grisly scene, and the cute ‘remember how the story began with a long car ride? There was a corpse in the trunk!!!’ twist. Oh, and I liked that while the family members are still pretty awful in different ways, they’re surprisingly on good terms in others, like the setup makes you expect an inheritance scheme on the part of the matriarach perhaps but instead she’s (momentarily) humbled when realizing how she hurt her grandson. But the connections hanging it all together seem pretty underdeveloped, and some characters seem like they’re barely explored if at all. I wonder how Yokomizo decided which doomed families were interesting enough to run with for a full novel and which could get slotted into a relatively quick twist setup like this.
I agree the stuff from the later setting like 金田一先生 and 等々力警部 were intriguing! It’ll be interesting to see if/when he’ll turn up now being tipped off that if he does he’s definitely a recurring character.
