The latest chapter is 21. And it's bi-monthly 'cause Yuri Hime is still a bi-monthly magazine.
I guess it still is, but what happened to the announcements saying it was gonna be monthly in 2016? :<
Well, the rumor says they're finally prepering to become monthly. But I don't know how they manage to do that if their new series like Shoujo Shikkaku, Last Waltz, Prince Prince, Sumedo Jigoku no Inferno ended recently and their endings looks rushed. Like editors just cut those series. All of them closed just in 2 volumes. Also Takemiya Jin will no longer be a regular in Yuri Hime :( So, YH editors have to bring new authors with good ideas for yuri stories or they will end up just with Yuru Yuri and Citrus in a monthly " yuri magazine."