Kisaragi's Sons

Kisaragi's Sons in GNG
Kisaragi’s sons met Chibi in the forest behind the valley. They fight him until Terry comes in and stops the fight. Kisaragi appears and fight Terry, but suddenly he hears that Ben's platoon is trying to escape the volcano crater and he leaves his sons alone, while he goes to stop the escape.

This became fatal, because while Kisaragi was away, his sons were killed by Akakabuto's soldiers.