I finished my second plushie! It took a while because I had to take my sewing machine died and I had to take it to Ikea somewhere halfway through. They did give me a new one immediately, which was a pleasant surprise after all of the possible doom scenarios I'd thought out on my way there (most of them involved waiting for at least another month).
I'm slightly less proud of this one than the Creeper I made since the face is slightly crooked, but still. I'm planning to make more of these in different sizes.
I didn't really use a tutorial but looked at some pictures of other people's onigiri plushies and drew my conclusions from those instead.