Toshiki Miyamizu is shown to be a very busy man and the estranged father of Mitsuha and Yotsuha Miyamizu. Following his wife's, Futaba's, death, he rejected the Miyamizu shrine and its traditions to pursue a career in politics. He became the mayor of Itomori two years after his wife's death and has held the position for four years as of 2013.

He was, under his daughter's suggestion, responsible for the evacuation of Itomori during the Comet Tiamat incident. As all residents survived, he was scrutinized by the media for some supposed "hidden agenda." It is unknown what happened to him at the end of the film, as no mention of him is made in the film past the Comet Tiamat incident.
(Source: Kimi no Na wa Wiki, edited)