Yui was deeply devoted to her sister-in-law, Ai, treating her like a real sister. Whenever she had free time, she would visit Ai and her husband at their home, enjoying each other's company. Ai trusted Yui completely; they could talk about anything and even help each other out with secrets that nobody else knew about. One day, after Ai went through a painful breakup, Yui comforted her by accidentally kissing her. From there, their relationship changed drastically... As Ai continued to rely on Yui, their bond grew stronger than ever before.

絢愛は兄の嫁のゆいの事を実の姉のように慕い暇があると兄夫婦の家に遊びに行っていた。絢愛は、ゆいには何でも話せて誰にも言えない相談にも乗ってもらい信頼していた。ある日、失恋で傷心した絢愛を慰めているうちにキスしてしまうゆい。そこから2人は今までとは違う関係になっていった…ゆいを信頼して身を委ねる絢愛。