Junjou Gal wa Kanojo ja Nai noni

One ordinary morning, an average high school boy named Asahi Hirakawa turns on the TV in the living room as he always does. The news begins airing a report from a hot spring, and it seems like another completely ordinary day is about to begin. That is, until a topless female reporter appears on screen...

Asahi soon discovers that society's views on male and female chastity have been completely reversed. Though bewildered at first, he tries his best to adapt to this upside-down world. Then, one of the most popular girls in his class, Riria Sotogahama, confides in him that she has no experience with men...

"Hirakawa-kun! Please! Just let me do it once!"

(Source: Kadokawa, translated)