Ayai adores her brother's wife, Yui, like her real sister, and goes to visit her brother's wife whenever she has free time. Ayai trusted her girlfriend Yui because she could talk to her about anything and even give her advice that she couldn't give to anyone else. One day, while comforting his girlfriend Ayai, who was heartbroken over her broken heart, Yui ends up kissing her. From then on, the two developed a different relationship than before... Ayai trusts Yui and entrusts herself to her.
