|Japanese name:||宮永 界|
|Family:|| Teru Miyanaga (Daughter)
Saki Miyanaga (Daughter)
|Debut:||Saki, round 3|
|Voiced by:||Onosaka Masaya|
|Live-action actor:||Tomoharu Hasegawa|
Kai has short brown hair and brown eyes with glasses. He has a slight beard.
Mr. Miyanaga lives in Nagano Prefecture with Saki, while his wife lives in Tokyo with their older daughter Teru. Although the two live separately, they are not divorced. He continues to pay attention to Teru's mahjong by reading reports on her matches in Weekly Mahjong Today.