Shame there's no good angle / demon yuri anime or manga out there :(
I don't know. Personally, while I find angles very fascinating, I just can't see how a mathematical concept could be yuri. Maybe that's why there's so little of it?
Ooh, I didn't know about Yuuko's birthday having been recently :o
I barely remember characters' birthdays when I look them up, and I never looked up Hibike characters' birthdays lol