Yup, I myself am surprised to see a fan of it as well. The historical backdrop, the characters, everything! The love between the two main characters is also complex and self-developing.
Yass so true! I love everything about it! I've always thought the way Sei fell for Okita was unique not typical. I wish they'd make an anime out of the manga. I have yet to read the rest after volume 16 or so because it's extremely hard to find translated copies ever since Shojo Beat was cancelled :(