Just curious, why do you think he began the assault with gloves on? If his finger prints were all over the inside of the house, at some point he obviously took them off.I also don't think this handkerchief technique gives us the killer's origin, added to my point that I'm not 100% the killer actually did this to begin with. Also, he was wearing gloves. Seems strange that he would employe the handkerchief and the gloves and yet still manage to cut himself so deeply. He was wearing gloves when he entered the house and when he began the assault. Wouldn't he think that was enough protection? Assuming, of course, he would know that knife slippage were even possible or likely?
I would also add, millions of Tokyoites will have handkerchiefs on them, they're sold at every konbini in the land, pretty much. Admittedly, use in the humid summers is far more common. But I had handkerchiefs on me while in Japan too and folding them around my blade wouldn't tell you I was half-British, half-Spanish any more than me eating spinach for lunch that day. Of course, I can't (and won't) discount the possibility of some sort of connection to a fish factory, whether Chinese or Filipino or not. But a Chinese or Filipino factory worker would need a way of getting in and out of the country undetected as well as a way of getting on to a US military base. So, until there is something stronger pointing to a factory, let alone one in China or the Philippines, I'm not convinced.
Re: a US military base.. I believe they had mostly been vacated by US military by the time of the murders, but there certainly were US bases in the northern Philippines (mentioned as a location possibly associated with unusual handkerchief folding) at one time. (Idk, I guess the waist pack would be too new to be associated with sand from an at-the-time-closed US military base in N Phillipines?)
And speaking of fingerprints..earlier this week there were several posts about: 1.) the 50 minutes (there may be an unknown / not-discussed reason that could explain the delay in calling police, but jmo, I think it is improbable that Haruko simply fainted), 2.) the problem with the noise discrepancy (nobody next door - apparently close to an open window - hears screaming, as three people are stabbed to death close to that window) and possible TMPD dissatisfaction with some of the information provided by those next door, and 3.) An’s son (time spent in UK, his age, and the possibility of a young person known to him).
You commented on the age range of any acquaintance - and of An’s son (being likely too young at around 13 - which I agree with), but you also said it would astound you if detectives didn’t “go through that kind of circle. [..] Though possible they did and simply didn’t fingerprint someone who had a good alibi or some such.”
What circle do you mean? Are you saying you don’t know whether An’s son was ever fingerprinted? I would find it hard to believe that TMPD didn’t collect fingerprints and DNA from everybody next door (incl An’s son - and husband if he present that night). Can you provide any clarification? Jmo and tia