Cut the carrots, boil to your desired firmness, drain in a sieve and let them cool down.
Mix all the ★ ingredients in a pickling jar and let sit (remove the seeds from the red chili pepper, and tear into pieces).
Pickle in the refrigerator for more than a night before eating.
Here they are in my daughter's bento. They also make great snacks.
Story Behind this Recipe
My mother often made these when I was in middle/high school, and they added color to my bento. These days, they're handy when I make my daughters' bentos.
Let the carrots cool completely after boiling, and be sure to drain the water before adding them to the pickling mixture. You can reuse the pickle juice 2-3 times. When there's only a little left, add sugar and mayo and use as salad dressing.