Dai is the father of Kei, Mai, Rie, and Yui.
At some point before the series, Dai helped raise his four pups with the help of Kokoa. He is seen to be a bit childish and likes to wrestle. During the series, Dai pretty much acted the same during their visit for the family reunion, but he knows when to be serious and comforting. He called up Kei later in the series when Kokoa went missing.