Ryo and Zen, who were in the same year in the sales department and had been rivals since their high school days, competed in all sorts of things.
In the midst of some drunken spree, they decided to become a couple after a silly competition: "Whoever make the other fall in love first wins."

The two still can't be completely honest with each other, but as Ryo and Zen continue their "competition" - a form of communication - they start to act a little more like a couple, but they're both so busy with work that they don't have time to spend together and they keep missing each other...

As they get jealous and anxious over trivial things and are tossed about by emotions they can't control, Ryo and Zen's colleague Futami, who has just returned from being transferred to the Osaka branch, asks to be included in their match---!?!?

The two become lovers, and restart their careers and love lives with an upgrade!!

Love slowly turns into love. Just the two of them, spending everyday like this.