Onigiri! The cutest food? Probably.
In all my years of watching Anime and attempting Japanese cuisine, I've never tried making rice balls. WHAT GIVES? They're super easy and very tasty! And the rice makes for a basic meal when you're experiencing tummy issues. Just Hungry has a great method for making onigiri, so I would start there.
We used leftover salmon, tuna with Kewpie mayo, and minced umeboshi for fillings, with sesame seeds and nori for toppings. Put a dab of the filling on top of the ball when you're done; it'll show you what's inside and it's super kawaii.