(from ebookjapan):

The city watchmen protect the security of Cologne, a bustling medieval metropolis. The young ace, Odo, is a man of great ability who is admired by his junior colleague, Fleet. However, a search ordered by the higher-ups to find someone to get rid of a problem turns into a big case...?

This is the story of "Brother Odo," a popular character in "Monk Falco," during his time as a public order official.