This one is so difficult, I have bunch of mangakas that I adore and tend to stalk their works xD. There is Nakamura Asumiko, Hidaka Shoko, Higashi Nishida, Motoni Modoru, Yamashita Tomoko, Yoshinaga Fumi and several others. There are two that are special for me and I can’t decide between them; Yoneda Kou and Suzuki Tsuta. But since I have to choose one it will be the mangaka that makes me the most excited when I see something new of her around: Suzuki Tsuta.
Her mangas are sexy and funny, the characters are great, there is a perfect amount of drama (just a bit) and she does some unexpected things sometimes. The stories are entertaining and there is a special feel in her narration. Sex is not exactly her selling point, but when she wants, she can do pretty smutty things. Oh and also cute things (cute oyajis lol). Besides her characters are usually manly; sometimes you have no idea who is going to top/bottom ^^. I have to stop ranting! more about wonderful Suzuki Tsuta in a mangaka post for the aguy_yaoi community.