Hirutu is the Chaka (chieftain) of the Kila and responsible for most nonmagical affairs of the people. Technically he is over the kiki as well, but it appears he generally allows them to manage their own affairs.
When the Son of Steelbeard arrives on Kila, he soon learns of a conflict between the shipwrecked pirates and the Kila. There are many aspects to this conflict, and Hirutu appears not to be responsible for all of them. For example, Asali refuses the pirates access to water from the waterfall, but after appeasing her they are allowed to draw water. Were this an order from Hirutu himself, it is unlikely appeasing Asali would change permission.
Although Hirutu may not have contributed to some aspects of the tension between his people and the pirates, he was a major contributor. He was, for instance, preparing to go to war based on visions of the village seer, Kiki Tenya. He also holds the pirate Slim prisoner, sentenced to death as a sacrifice for their Hike (ancestors). During the quest "On the Warpath," he refuses to listen to the Son of Steelbeard. He changes his mind only after a possessed Makoto presents several prominent villagers' opinions against such action.