I’ve made and looked at a lot of fukus over the years and the question I get the most is about the sleeves. I thought I’d type up some basic info on how I make mine in the hopes that it helps someone further on down the road! This isn’t really a step-by-step tutorial since… I don’t really think it needs to be.
For fuku sleeves use white foam sandwiched between layers of fabric. Since the bodysuit part of the fuku is white, the foam you use should really be white as well- the green and tan foam will show through most white fabrics and won’t look right.
I cut a sort of pointed oval shape out of foam and fabric. Place the fabric on top of the foam and fold from point to point- sandwiching the foam in between the fabric. The folded edge is the outer part of your sleeve. Pin and baste the foam-and-fabric-sandwich together along the raw edge. Then simply top stitch with white thread and you’ve got some swanky outer-space-y looking sleeves for your fuku.
If you have trouble finding the foam, I sell it here.