Kanojo no Idea

Ever since middle school, Hinata has been a huge fan Sumika Nayuki, an actress of her same age. Now in high school, Hinata ran into Sumika on the street, and was shocked to find her idol's real-life behavior to be very different from the public persona that Hinata worshiped.

(Source: Kadokawa, translated)

Note: Chapter count includes 16 regular chapters and 3 extras.