Cut chicken tenders into bite-sized pieces.
Slice the onion thinly.
Beat the eggs in a bowl.
Heat oil in a pan and stir-fry the chicken tenders.
When the chicken is cooked, add the onion and stir-fry together.
Add soy sauce, mirin, and sugar to season.
Pour the eggs in and cook gently over low heat.
Serve over rice to finish.