小清水亜美
is an officer from Nagano Prefecture Police and Kansuke Yamato's childhood friend and is secretly in love with him. She is the opposite of Kansuke and is professional and considerate to others. When Kansuke was presumed dead, Yui resigns and takes it upon herself to marry into the family to investigate the death of another well-loved colleague. She later rejoins the force. Her Japanese voice actress is Ami Koshimizu.