Upon graduating from university, Mirai married her childhood friend and spent her days living a happy married life. She and her husband are close friends with a certain young man who's from the same university and who's also her husband's junior at work. However, on the other hand her husband's opinion of him is that he's a womanizer and an irresponsible man.

The young man begins plotting after seeing that he has gained Mirai's full trust. Before him is a wife who let her guard down and a husband who just keeps working overtime for some reason... From his point of view, he couldn't see her as anything but prey.

"The truth is I... I've always liked you, Mirai-senpai..."

One day, Mirai began to dwell on the words of their junior who seemingly spoke without thinking. She started feeling guilty over not realizing his feelings back when they were still students. He was exploiting a gap in Mirai's defenses. Did he see through her and manage to read her true feelings?

"You're so mean, senpai..."
'Eh? Mean? Me?'

He was taking advantage of her guilt using deceitful words, which made her relent and let him take her to bed despite the fact that she has a husband. Sex with him was completely different than with her husband, to the point that her sense of reasoning seemed like it was going to break. And so the number of secrets that she had to keep from her husband began to grow...

(Source: DLsite)