Bring a pot of water to boil and cook soba noodles according to package directions, then drain and set aside.
Cut chicken breast into bite-sized pieces and season with sea salt and black pepper.
In a small bowl, whisk together gochujang, tamari, rice vinegar, minced garlic, and grated ginger to create the spicy glaze.
Heat sesame oil in a large skillet or wok over medium-high heat.
Add chicken to the skillet and sear until golden brown and cooked through, about 5-6 minutes.
Toss in broccoli florets and sliced red bell peppers, sautéing for 3-4 minutes until the vegetables are tender-crisp.
Pour the gochujang glaze over the chicken and vegetables, stirring constantly until the sauce thickens and coats everything evenly.
Add the cooked soba noodles to the skillet, tossing gently to combine and warm through.
Garnish with sliced green onions before serving hot.