Cut chicken breast, onion, and bell pepper into bite-sized pieces.
Rinse konjac noodles in water and drain well.
Heat olive oil in a pan and sauté onion and bell pepper.
Add chicken breast and stir-fry until cooked.
Add konjac noodles and mix quickly.
Add tomato sauce and continue stir-frying over medium heat.
Season with salt and pepper, then plate.