Kuronagi Mikoto, a student in her first year of high school, is irritated. This is because her older brother of two years, Kuronagi Wakazumi, is becoming increasingly overprotective and meddlesome. As the president of the Japanese Archery Club with both an attractive face and figure, he is very popular with the female students. She wonders why he is so strict with her, even though he has a kind attitude towards other girls. One rainy day, Mikoto relays her concerns to the school nurse, Nikaidou Shinobu. Nikaidou sneaks his way into the holes of Mikoto's heart like a gentle, quiet rain shower... From then on, the the relationship between Mikoto and Wakazumi gradually begins to change. It's the rainy season. Hidden feelings begin to pour down without pause... [Translated from [url=http://www.dlsite.com/girls/work/=/product_id/RJ120257.html]DLsite[/url]]

The protagonist, Kuronagi Mikoto, is such a hardcore brocon that her friends often make fun of her for it. In particular, she has special feelings for her oldest brother, Soushi. On Christmas Eve, Mikoto happens to see Soushi walking along with a lady whom appeared to be his lover and gets quite the shock. Soushi's lover, Tatsumi Rinko, studies in the same university laboratory as him. Since Rinko has an "adult" air about her that Mikoto doesn't, Mikoto becomes restless and jealous of her. She then realises that the feelings she have for Soushi isn't simple brotherly love. Even though she knows that he's her biological older brother, her taboo feelings keep on growing... Also, Mikoto's other older brother, Wakazumi's feelings for her are also growing stronger and...? Where will the three's entangled feelings lead them? [Translation of the official website's story summary.]