I might be overthinking it, but...
1. Parts of southern japan used to be settled by austronesian that later integrates with other japanese people
2. Tattoos are/were huge part of austronesian cultures, from taiwanese aborigines to the maori, they wore extensive tattooing throughout their body as part of their culture
3. Apparently one of the chinese description of early austronesian is the barbarians that keep their hair cut short and untied, unlike civilized chinese that grows their hair out and tie it in an exquisite manner
All three are mentioned in the chapter as the difference between them and native japanese
Huge expansion of narrative scope and ambition in the last few chapters. Time travel of various sorts, overlapping yet divergent realities ("fates"), metafictional self-awareness and play, rhyming themes and details. Lots of fun, though at times head-spinning. Will clearly require another read, once I've caught up.
..... Wait, this snake is the same Kippuuson from chapter 1 and the other bonus chapter??? Why did his appearance change so much while the spider kami stayed pretty much the same??