My thoughts on various topics here.
1) The 2nd perp theory has literally no evidence.
I don’t even know for what exactly we need a 2nd perp. We can extend that to 3,4,5,6 folks all standing outside the house, unseen and unnoticed. Imo, zero evidence links to a 2nd guy involved. Infact this would be even more incredibly shoddy if there are 2 or more guys involved here.
2) Re: clothes - I don’t mind the theory that the killer could be a random Japanese guy. One reason why so many believe in the foreign military brat is coz of the sand and the killer not getting apprehended despite the TMPD. And yet the latter part could be completely a matte of luck/ chance and as far as the sand thing, the Miyazawas have been to the exact same places. So it isn’t exactly uncommon for a Japanese guy to have that kinda sand in my view.
It is however super interesting that he doesn’t attempt to destroy his stuff in any way. No burning, throwing them in cola, detergent, submersion, pooping, or any sort of thing.
No attempt whatsoever, despite the fact that he does infact sully some documents and the belongings of the Miyazawas. That shows some incredible confidence from a presumably first time killer about him not being traced.
3) Re: sanitary pads being natural to use to stop bleeding.
I beg to differ here. It would have been much easier for the killer to use his own handkerchief (he has two with him) or Miyazawas clothes from inside their cupboards. Even if he had concerns about sterility, he could have simply heated them in boiling water, or doused them in some kinda antiseptic.
These kinds of methods are what are shown in movies or pop culture in nomal life. If someone did this, especially if they are actively bleeding out, then I would consider this to be far more usual than anyone actively seeking out sanitary pads that weren’t even readily available to the killer.
4) the abduction or SA of the kids motive also doesn’t make much sense to me. Ultimately the killer had the opportunity to do more evil stuff and he didn’t (thankfully) so attributing this to his already gruesome crimes seems like an overreach to me.
5) the killer doesn’t demonstrate any good method of grappling one on one. Infact he is afraid to go after the mom and the young girl with his broken knife. I highly doubt this is someone skilled in any kind of combat skills.
It is more than likely his upper body strength comes from some different kinda activity- possibly something like tennis.