Such beautiful work! I love the small pieces of work all assembled together in the quilts. As far as finding books in Japanese, ask in your library if there is an area for foreign language books. There usually are books in many different languages. I love Japanese quilting books! I am not for using an exact pattern or recipe, but inspiration from other cultures are wonderful!
Very interesting and lovely projects and I appreciate the amount of woek these must have taken I am currently in Japan easy to find materials hard to find a teacher sadly. Sashiko was origianlly used because the poor people which explains why it is often thrifted. That said I am slightly confused why you think it is pronounced Sashko. From what I understand from my basic studies here in Japanese the sounds of the letter sets similar to Welsh do not ever change. The letter sets always have a vowel at the end but the sound of the I is different to English the Shi her sounds more like a British She thsn what we may say as Shy so with a short quick e on it so it is in fact it would be said as SaSheKo. Maybe it hard for someone Scottish because the Scottish sometimes sound much longer snd softer on vowels.
18:24 i have a tool that looks exactly like this pink "thingy." It's for sculpting clay, it came in a kit with a few other tools, but mine has a sharp point. Tools with a small ball at the end ARE sold for sculpting, but also more-so with paper embossing supplies.
