Prologue:

A romantic relationship only belongs to two people and nothing more.

I don't intended to be a third party when two couples break-up. My intention is to just live a quiet and hassle-free life. I was just your ordinary next-door neighbor, a common person with no redeeming qualities. But then....

"I want you to sleep with my girlfriend... and let me watch you two do it!"

One day in my life, an offer I never expect to get suddenly came. A girl who is in a relationship with a girl offering something I didn't imagine could happen. And then...