½ cup sweet Japanese plum wine
¼ cup soy sauce (such as Kikkoman®)
¼ cup clover honey
1 bunch green onions, finely chopped, or to taste
2 cloves garlic, finely chopped
1 pinch cracked black pepper to taste
3 eaches skinless, boneless chicken breast halves
Combine plum wine, soy sauce, honey, green onions, garlic, and black pepper in a resealable plastic bag; seal and massage bag to thoroughly mix marinade.
Using a fork or meat tenderizer, score chicken lightly without pounding. Add chicken to marinade, massage gently to coat, squeeze out excess air, and seal the bag. Marinate in the refrigerator for 20 minutes.
Preheat an outdoor grill for medium-high heat and lightly oil the grate. Remove chicken from the marinade and shake off excess. Discard the remaining marinade.
Cook chicken on the preheated grill until no longer pink in the center and the juices run clear, 5 to 10 minutes per side. An instant-read thermometer inserted into the center should read at least 165 degrees F (74 degrees C).