Tsutsukakushi Tsukiko

Referred to as younger sister by Youto. Her wish to the Stony Cat was to not show her emotions so easily, because she was a crybaby. As a result, she has become unable to express any emotions whatsoever, regardless of what she is trying to say. It is hinted that she may have feelings for Youto, but this is difficult to determine since she is not able to show her emotions.