The Poison-Slicing Sword (斬毒刀 Ki Dokutō?) was a dao from the Joketsuzoku village that could give a loud verbal warning of any nearby poison through a flower with a mouth at its tip. The sword could also slice through any poison, but could only do this once.
Cologne gave the sword to Ranma Saotome along with the Poison-Crushing Shield to rescue Shampoo after she had been captured by Pink & Link. After the twins revealed that they were holding Shampoo atop a flow at the end of a massive vine, Ranma began to climb the vine. When sprouts on the stalk began to open, the sword cried out that poison was coming and Ranma tried to slice through the cloud. However the sword pulled itself back, forcing him to use the shield to block the poison. When the sword breathed a sigh of relief it was berated, but issued more warnings as Ranma climbed.
When he got to the flower he used the reverse edge of the blade to hit the twins after foiling their first poison attack with the shield. However they then recognised the shield and Link poured some stomach, eye, and cold medicine onto it, shattering it. The twins followed up with a third attack and Ranma forced the sword to cut through their poison cloud. However the flower then said its last words and fell off, rendering the sword's ability to cut through poison useless as Pink and Link confirmed that it could only be used once. It was apparently lost when the twins used the flower to relocate to Furinkan High School and sow a forest of poisonous plants.