Dream of the Kappa: Part 2

As Conan investigates, he realizes how the culprit was able to drown Bonzou with swamp water in his own attic. Conan tranquilizes Yamamura and reveals the murderer to be Tokobi. Conan explains combining the water bottle and the paint bottles would be able to carry enough swamp water to commit the crime; The water was then poured into a basin where Bonzou was suffocated in. This is evidenced by the diluted paint that are currently in the containers.