Shota was looking forward to meeting his older sister, Nanami, at his friend's house, Kohei, who he often visits. The reason is that Nana actually has huge breasts that are popular in the neighborhood, and she is an irresistibly attractive older sister for Shota, who has no eyes on her boins. One day, while Shota and Kohei are talking about a sex education class they learned at school, Nanami suddenly joins them...
