妻交換～あいつのワイフと俺の嫁～

Takumi Araida has been married for 3 years. He loves his wife, but he feels troubled that their married life has become monotonous.

One day, a married couple moved to the apartment next door. Surprisingly the wife was Ryouko Nakajima, Takumi's classmate in middle school, and her husband happens to be Takumi's wife's acquaintance. In celebration of their reunion with old acquaintances, as well as the Nakajima's moving into their new residence, the two couples held a party.

Eventually everyone got drunk and dozed off except Takumi, and as he was clearing up and bringing the utensils into the kitchen, Ryouko alone woke up and came to him. It was then that he cut his fingers while he was cleaning up. After he washed off the blood, to stop the bleeding Ryouko suddenly sucked on his fingers.