Rinse sushi rice under cold water until water runs clear. Cook according to rice cooker instructions (about 20 minutes). Transfer to a bowl, add salt and furikake, and cool to room temperature.

Cut chicken into small pieces. In a bowl, mix soy sauce, sake, baking soda, and cornstarch. Add chicken, coat well, cover, and refrigerate for 30 minutes.

In a small bowl, whisk soy sauce, mirin, and brown sugar until dissolved to create teriyaki sauce. Set aside.

Heat oil in a skillet over medium-high heat. Add marinated chicken and cook for 2-3 minutes until golden brown. Stir frequently. Add minced garlic in the last 30 seconds, then pour in teriyaki sauce and stir until thickened (about 1-2 minutes).

Wet hands and mold rice into a small triangle, creating a well in the center. Fill with cooked chicken, fold rice over, and compress gently to seal.

Wrap nori around one edge of each onigiri and repeat with remaining ingredients.