Yuu, the younger brother, and Miu, the older sister:
Miu showered her brother with so much affection, her love overflowing and bountiful. However, their parents became concerned with her constant doting.
Thus, the only solution was to send Miu away to prevent any misfortunes. And so, her life as a boarding student began.
The ever-so close sibling bond was broken.
Years went by with no communication between them whatsoever, but Miu finally returned home, having at long last graduated from the boarding school.
Yuu, upon her return, was instantly captivated by her beauty, her body growing only more splendid with every passing year.
Nonetheless, her attitude took a complete shift. The former loving and caring older sister was now cold and distant.
As fate would have it, Miu, in all actuality, hadn't changed one bit.
The star-crossed siblings, reunited under the same roof, were separated no more.
With their parents around, Miu was forced to put up a wall between Yuu and herself, barricading her true emotions. However, whenever their parents left, Miu's change in personality was instantaneous.
Unfortunately, Yuu was cautious. He wanted to make amends. To this day, he still blames himself for his sister's sudden and forced transfer to the boarding school. His desire to rekindle their former relationship was heavily outweighed by his immense guilt.
With each passing day, Miu's desire for her younger brother grew and she became impatient. Backed into a corner, her final resort was to lure her younger brother with her feminine charms.
Eyes at the ready, she carefully observed her prey, eager to pounce when her younger brother could no longer suppress his sexual urges.
And thus, the two siblings would spend their days enraptured in the husky aroma of sex and love...
[Translated from the description from DMM]