Ken Mitsuishi (光石ケン, Mitsuishi Ken) is the father of Dan Mitsuishi. He was a Marie Antoinette fan that was created by Ruby's Father. 30 years ago, he asked the father of Ruby to create the seven pieces of Cat's Eye jewellery because he wanted to give it to his wife the kind of jewellery Marie Antoinette worn. Ken has sealed the jewellery after the death of their creator.