1x601 - Case Closed

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. Tokobi professes to the murder and exclaims Bonzou ordered his son to disguise himself as a kappa and play in the river in order to attract customers to the inn. Conan clears the misunderstanding, explaining that Tatsuhiko must have done it on his own accord in secret since he burrowed a paint set from Tokobi instead of buying paint himself. Araiwa confirms Conan's deductions, explaining how Bonzou removed Tatsuhiko's disguise as to not shame his son after his death.