Step 1: Cook a rice with slightly less amount of water, salt it a little and let it cool until it’s cold. Wet your hands, take about hand of rice and with your finger make a hole to the centre. Put there some tuna and close opening with a bit of rice. Use your hands to shape rice into triangles (if you’re unable to do it, you can shape it into simple balls). Use scissors to cut a strip from nori and stick it to onigiri (optional, but it makes difference. You can for example cover it with sesame seeds instead). Let it cool in fridge for some time. Enjoy!
Step 3: note: i often sprinkle on it soy sauce and add some wasabi because i like it that way, and you can see it on picture too, so i’m sorry they look so weird :p