虜ノ旋律 ～淫らに喘ぐ処女セクステット～

Nao is a second-year student at the famous private school, Seirenjou Academy. She is the president of the school's string orchestra club, which her best friends Chizuru and Riria are also members of, and she has a fulfilling school life. Aside from the two, the club also consists of Nao's younger sister Mai, their senpai Tsubaki and Mai's friend Ayumi.

These girls form a sextet, and they are practicing for an important competition that will be held about in a month, which is said to be a gateway for young musicians. If the girls win it, they'll earn a scholarship at a famous music school outseas, which is a huge opportunity for Mai, who is aiming to become a professional pianist. The girls train hard with the help of Souta, who is Chizuru's older brother, and who happens to have knowledge of music.

However, there happens to be one problem: as the music room, where the girls practice, is used by the brass band as well, they cannot practice there as they please.
Souta comes up with an idea: during the days they can't practice at their school, they should come to practice at Teirei Academy's music room, which is the school he attends as a third-year student.

Although the preparations for the competition were coming along smoothly, Nao was worried about a few things.
One of them is Teirei Academy's student council vice president, Kijima Shou. Though he appears to be a good person, Nao can't stand his carefree and inappropriate attitude and tries her best to avoid him, but unfortunately runs into him numerous times when they are renting the music room.
And as of lately, she has felt like somebody has been stalking her - which both Mai and Tsubaki have also seemed to notice. Despite her fear and anxieties, the accuracy and overall quality of her performances has increased.

But then, one day, Nao's deepest fears become reality in the worst way possible--
She is taken down by two men and raped, after which she is forced to endure days full of torment and humiliation in order to protect her sister and friends.