There's this thing with Japanese manga: comics for boys are mostly created by male authors, comics for girls by female authors. Usually, when you read the notes and comments where the authors talk to their readers, it becomes evident that they expect the readers to be of a certain gender. Look at the yuri manga in this website: a large majority are authored by ladies, and when they talk to their readers they call them "cute" and discuss with them female fashion and makeup and what to do if you fall in love with another girl. Sometimes they give them tips about how to find clubs or brothels that cater to lesbians!
The easiest way to find which is the intended readership for a work of manga is to find what the mangaka has to say about that. They almost always have a very definite idea on the subject. Sometimes they add "oh but it's ok if other people also want to read my stories!" but this of course also makes clear who they're actually making manga for.
Right now, it seems to me like all the authors whose works I read write primarily for girls—both Chinese authors like Xian Jun or Tracy Hu, and Japanese authors like Morishima Akiko, Shimura Takako, Morinaga Milk, Yatosaki Haru, Odoroo Dorothy, Yurikago, Hijiki, Iwami Kiyoko, Kosuzume, Tamamusi, etc.