Murder Princess: Volume 1 (Murder Princess) - Sekihiko Inui

The world of politics is treacherous enough, but in Forland, it's deadly confusing. When her royal father is murdered by a greedy drug manufacturer, Princess Alita must step forward to take over the kingdom. Unfortunately, a freak magical mishap has trapped her in the body of Falis, the bounty hunter. Now Alita must stay disguised as a servant while the battle-savvy Falis sits on the throne in her body! Threatened by a coup and attacks from the outside, the fate of the kingdom is in the hands of Alita and Falis. Switched souls or not, there's another royal heir and Alita has to hold everything together for a little longer. As though this weren't enough to juggle, evil Professor Akamashi and his twin android assassins are out to cause some trouble of their own.