Shoujo Mangaka no Koi (OSAKABE Mashin)

From Celestial Scans & WoC Scans:
This story is about a cute shoujo manga artist, called Otome ("maiden"), and her manager Ouji ("prince"). Her works aren't very popular, so Ouji had to become her manager to help her boost up her popularity. Of course, he's hot, young, a genius, and as her manager, he has to live with her to make sure she keeps her deadlines and comes up with interesting ideas and adorable characters. But when her works DO become popular, he is replaced on the job by his ex-girlfriend... and that's just the beginning!