Has an NPB (Japan) game ever ended 15-7?
Yes. NPB (Japan) has seen a final score of 15-7 26 times. It first happened on June 23, 1956, when Hankyu Braves beat Kintetsu Pearls, and most recently on May 14, 2023, when Hanshin Tigers beat Yokohama DeNA Baystars.
That makes 15-7 the 107th most common final score out of 223 that have ever occurred in NPB (Japan). One point away, 16-7 has happened 8 times and 15-8 has happened 16 times.