Ayane adores her brother's wife, Yui No, as if she were her own sister, and whenever she has free time she visits her brother and his wife's house. Ayane trusts Yui, who she can talk to about anything and who will listen to her problems that she can't tell anyone else about. One day, while comforting Ayane, who is heartbroken after a breakup, Yui kisses her. From then on, the two of them have a different relationship than before... Ayane trusts Yui and entrusts herself to her.