ガンガン生射ち！お兄ちゃん、ボク、××しちゃうっ!!

The protagonist, Toshio Maekawa, is an unconventional third grader student who is in science major anywhere, and it is a virgin kun.
Such he was to work as a tutor during the summer vacation.

The other party to teach is the curious girl "Mami" who goes to a famous private school,
Somehow live in the neighborhood of Shun man's house, a cheerful girl called Sanae who calls him an older brother.
The place to teach is a resort apartment in midsummer owned by the father of "Mami". Besides, it is a study camp in the night.
At first, Toshio also seriously taught them to study,
If a man and a woman live under the same roof, it will be decided naturally. The innocent girls at first were played with mere curiosity, but the act of the Shun was gradually escalated.