Ecchi na no wa Watashi no Sei ja Arimasen: Shojo nanoni Toshishita Idol no Kyuuai ga Omo Sugimasu!

I never believed that my favorite idol was a incubus and was crazy about me (and my energy)!

The overly earnest virgin office lady, Fuka, lives for the sole purpose of supporting her favorite idol, Ichijoji Ruka. One day, she is suddenly kidnapped by a mysterious man and forced to do naughty things. To her surprise, the man's true identity is her favorite idol, Ruka. Ruka is actually not human, but a incubus, and they end up doing "pleasant things" in a relationship, hoping to get the ultimate orgasmic energy that Fuka gives off, but...

(Source: Kadokawa, translated)