Why is Hirunaka no Ryuusei so popular?

so i've read this manga before and i think it's not >that< great but then i found out that this manga is so popular especially on tumblr, there are so many romance manga that's way better than this one but why Hirunaka no Ryuusei?

tumblr wants to fuck ugly old men

iknorite, Cheecky Vampire is much better