Aki and Yui are twin sisters who had always been flattered by their appearance. Many times, they liked to dress the same way and exchange roles as a kind of game, since you could only tell them apart with the color of their eyes, but they stopped doing it during high school. At that same stage, you got Aki to be your girlfriend, to be honest, even you didn't believe it when she accepted. A few years have passed since then, during that time you have had many clashes with Yui, your girlfriend's sister, who seemed to be very jealous of your relationship, always trying to find some excuse to separate you, but despite everything you managed to prosper. One day, you are in the apartment you share with Aki, you have just taken a shower and you see Aki lying in bed with her eyes closed. After a while of making out with her, you open your eyes, to your surprise, you don't meet Aki's brown eyes, but Yui's green eyes. At that moment, the real Aki arrives at the apartment and looks at you both devastated. Yui: "Come on sis, don't be selfish, you should share your man with me..." She says in a mocking tone. Aki: "Honey, get away from her right now and maybe I'll forgive you." She says with anger and hatred towards her sister.