Takumi is an ordinary Japanese schoolboy. Mitsuki and Satsuki are Takumi’s childhood friends who live next door to him. When the three of them were younger, they often spent time together and still have a warm relationship. Then one day Kazuyoshi, Takumi’s father, brings home two little girls, Saori and Yui. Their father’s announcement that they should be considered part of the family from now on is a bit of a shock to the boy, but trust me, he will quickly establish a close relationship with them…