An old school yakuza, Nagamasa Ryumatsu, ended up losing his life due to certain circumstances. But, when he awakened to a strange sort of scenery he had never seen before, he found that he had somehow changed into a beautiful girl!?

This is a story from the early 17th century, where everything was still in chaos.
A Story about Judicial Duels, and the law and order that will be introduced...
In the Holy Roman Empire that rules all of the Europe Continent...

Monju is a prototype of a line of anti-crime police robots, and he was an elite, celebrated member of the force. Now, to his dismay, he's been re-assigned out in the country, working alongside Yamagashi Junpei, a young cop who is mostly concerned with sexy women and his possibly thinning hair. Monju's combat capabilities seem unnecessary for a small town with its small crimes, and the people don't initially welcome him. Monju will have to find his place in this new situation, and win over the people around him with his skill for protecting the innocent. The first major case he must solve is catching an underwear thief, who Monju suspects might actually be the perverted Junpei. Will the two of them be able to catch the thief and clear Junpei's name?

From MangaHelpers:
In a world where humanity has turned into prey against the so called "white skin" creatures, one legendary figure known simply as "Ryuma" continues to give hope to this post-apocalyptic society. This individual has many faces and descriptions, but his/her legend has lived continuously in the hearts and minds of the people for half a century. No one knows where this legend started or who started it. Here starts a chronicle to unveil the mysteries of a legend.