Preheat a skillet over medium heat. Add the olive oil, chicken, salt, and black pepper. Stir to combine and saute until the chicken is cooked through and started to brown just slightly. This step should take 5-7 minutes.
Next, add the asparagus and butter. Stir to combine into the chicken. Saute until the asparagus is just tender - about 3-5 minutes depending on the thickness of your asparagus.
At this point, add the dried red chili flakes, if using. Pour in the teriyaki sauce and stir to combine. Cook until the sauce is heated through.
Turn off the heat. Add the sesame seeds and sesame oil Stir to combine.