The Honorable Swords are a decorative item that was obtained during the Treasures of Tokuno events. They are classified as a Minor Tokuno Artifact.
Whenever the events are active, the Minor Artifacts can be obtained by slaying creatures around the Tokuno Islands (with the exception of Cranes). The more creatures killed, the more likely an artifact would appear in your pack upon defeating the next foe.
If you have 10 such Minor Tokuno Artifacts, they can be "returned" to Ihara Soko the Imperial Minister of Trade in exchange for a Major Tokuno Artifact (even if they have been damaged through use).