Makoto, the protagonist, is an only child and is often jealous of his friends who have older sisters.
The older sisters of his friends look very sexy, and every time the protagonist burns with desire to get his own "big sister".
The defenseless Makoto is quiet, obedient and submissive, and when he sees something inappropriate, he immediately becomes aroused,
He is looked up to by "lonely" older sisters whose younger brothers have left them, and by older sisters who only had an older brother and wish they had a younger brother.
He is pranked by the older sisters, who turn out to be even more mischievous than he had imagined.
