Sarashina Subaru-Kun No Meirei Wa Zettai! ! summary:

"You're mine." She finds herself perched on his lap, on the receiving end of a steamy kiss. On top of that, he's carrying her bridal-style to a bed...! Hatoko's getting sick and tired of being pushed around by her childhood friend and professional model, Subaru (a.k.a. The Sadistic Prince). One day Subaru drags her along to... a photo studio!? Filling in for a model, she is forced to play the role of Subaru's girlfriend. Amid the confusion, Subaru tells her he loves her as his face gets closer to hers... How is she supposed to react when he's looking at her like that!? Her heart's hammering in her chest...!!