Bokutachi wa Hanshoku wo Yameta

The third year university student Shin Momotari dreams of creating the greatest movie, and one day he has a chance encounter with Hitomi Oosako, a girl beautiful enough to be mistaken as an actress. And, it just so happens that she is an entering student at the university Shin attends. Guided by fate, the two of them gradually begin to fall for the other. However, there is something that neither of them know. The partner that they've fallen in love with is related to them by blood, their sibling. And so opens the curtain on a pure and forbidden love story, woven by the two who must never be together.

(Source: Kodansha, translated)