From 1586 to 1587, his father and his elder brother Kikkawa Motonaga both died and he became the head of Kikkawa clan. Around this time, he changed his name to "Hiroie". Unlike his father and his elder brother who was known for the battlefield bravery, Hiroie preferred strategy and diplomacy to win on a battlefield and was highly praised by Hideyoshi for holding the Mōri clan together after the death of Kobayakawa Takakage. During the Seven-Year Korean War, he is noted for the defeat of a much larger Ming army at the battle of Ulsan castle.