"I'm in real love with you."
Mayori changed everything with that one statement.

Her big brother (protagonist) was already in shock from finding out Nanana, his pupil, had a crush on him.

Then Mayori declared she'll deal with all his sperm-related urges.

What follows is a bewildering, blood-pumping sexual ride half by force as he learns about love and sex---.

If there's love between two people, labels don't matter. Teacher and student. Brother and sister. A three-way harem is absolutely no problem at all! Cum yourself silly with spunk-obsessed Mayori!

[From DLsite English]