Mujikaku na Osananajimi to Kyoumi Honi de Yatte Mitara THE ANIMATION

Meiko, a beautiful, quiet, and academically gifted classmate, only shows her relaxed side in front of her childhood friend, Hiroki. Today, she comes to his room to hang out, and Hiroki can't help but glance at her body as she relaxes in light clothing. When she points it out, Hiroki blushes with embarrassment, but Meiko unexpectedly asks, "Well, do you want to touch me?" Their curiosity leads them to explore each other's bodies, which eventually escalates to sex...

(Source: PinkPineapple, translated)