Karisome Chouhi no Pride: Kouguu ni Saku Hana wa Mirai wo Koinegau

Amidst the intrigue of imperial succession, the fourth princess, Via, is worried. Her adopted father, the lustful emperor, has insinuated that she should become his concubine. Until now, Via has been living inconspicuously pretending to be weak and sickly, but her situation will only worsen if she stays put. So she decided to offer herself to the crown prince Alec as a concubine for a limited time in a marriage of convenience...?
Appearing like a fragile beauty on the outside, but strong and intelligent on the inside, Via charms everyone around her and she will have the power of the crown prince on her side!

(Source: Zero-Sum Online, translated)