What do you do after the sumo runs on the bridge in red dragon?

If you have not yet caught the kappa fish under the bridge, you can do that using the Rotten Fish.

The startled girl on the bridge has dropped some Bonsai Scissors. Pick them up and go back to the Bonsai hut to trim a bonsai. Otherwise when you go to the Sumo arena, they will say the Yokozuna (champion) won't fight without a bonsai.