However, a good food when you're in a rush is onigiri or rice ball. There are many different kinds of onigiri. Some have wasabi, fish, seaweed, meat and some are just seasoned with soy sauce.
You can buy onigiri almost anywhere. I usually make my own onigiri or buy it at a conbini or convenient store on the way to work.
I really liked it! Onigiri was the first food I tried when I came to Japan in 2018. The one I had was made of white rice with a seaweed filling and wrapped in a sheet of seaweed.
One way of preparing onigiri is by taking freshly cooked white rice, mixing in seasoning and wrapping it in cling wrap. With the rice all wrapped, you can shape it into a triangle. Unwrap and eat! Once the rice is cooked, making onigiri takes less than five minutes. I made a little video on how to make onigiri and you can check it out here: https://youtu.be/5OIZOYQ-0dg
Most of the ingredients are from Japan. However, Japan does import rice from other countries.