 No it doesn't - it can be round, or cylinder shaped, or anything else. There are a few purists who insist that onigiri must be triangular, but I'm not one of them. See Onigiri on parade.  No it doesn't - it can be round, or cylinder shaped, or anything else. There are a few purists who insist that onigiri must be triangular, but I'm not one of them. See Onigiri on parade. 