The Japanese teacher at my work lent me a yukata so I could see how it was made. This helped me make sense of the bizarro pattern pieces, although being an adult's yukata it was different from the one in my pattern, which had the tucks at the shoulders and waist which - I have since figured out - are there to allow the garment to be let out as the child grows.
this series of posts on sewing a child's yukata was helpful). I even changed things up a little and used French seams so it would look neater from the inside. Then came the obi. I found some dimensions from a shop selling them on Rakuten, and, using some soft voile from my stash, sewed a giant sash (basically a massive long rectangle). Things were so rushed in the lead-up to the 'big day' that I didn't have time to try the outfit on R in advance, but in the morning I used this tutorial to help me tie the obi.
kanzashi hair ornaments on the internet and ambitiously had a go at making my own, but after two ribbon flowers I'd had enough. Cutting and gluing tiny bits of ribbon is really not my forte, but luckily the two I managed to make before giving up looked quite nice when attached to a two-dollar shop headband, and R was thrilled with her new accessory.
At school I watched R walk around, smiling sweetly as people admired her outfit. She continued to be a sweet little Japanese girl even after she came home that day, and I thoroughly enjoyed watching her bow to me and pretend to be polite! Given the generous tucks in R's yukata (meaning that it is likely to fit her forever) I'm not expecting to have to make another, but since I've got a grip on the general construction principles I think I'll have a go at a jinbei, which has a very similar top section. I just have to find the right fabric and finish a few WIPs first...