Ryuu no Hanawazurai

Teenage Shakuya is the next head of the Dragon Clan – and she can actually turn into a real dragon. As if that's not enough, she also finds herself with two fiancés! The first vanished years ago and has now returned, but the new guy is not about to step aside. So Shakuya will wait a year, then marry the man she loves the most. Magic tattoos on both of Shakuya's hands, will help her to decide. Each one represents one of her suitors and as her love grows, so do her tattoos!

(Source: CMX)

Included one-shots:
Volume 2: Haguruma Tsukai (The Cogwheeler)
Volume 3: Double Crown