Took a basic shirt pattern, altered it, and made my own sailor collar pattern. I kept the arms "loose" because that's how it appeared to me in the reference images. Skirt is a box-pleated skirt with 2 inch pleats.

For the hat I just took a big circle and hand gathered it. I glued it onto the blue band and sewed that onto my wig. Neck tie was just an elongated diamond shape that I sewed together.

I used cotton sateen, which was great for the shirt and not so great for the skirt. All the navy pieces were made of stretch twill which was leftover fabric from when I made Mirai.