As Jin's monsters mobbed up the Demon Rat horde with their surprise attack, there were a few casualties on their side. Mainly the Mousefolk as they tried to assassinate the retreating Demon Rats.
While those sentient looking mice were nimble and agile, most of them could not handle more than a hit or two from the enhanced demon rats with their steampunk technology. However, it was also thanks to their small build, providing them with great speed and agility that allowed them to crawl to their weak points, their tails. (Most of them were only thirty centimetres tall!)
Cutting a demon rat's tail was similar to cutting the carotid artery of a human being. Slash that part away, and the farm rats would go into a nervous breakdown which eventually paralysed them, making them unable to breathe. Thus, they would die from suffocating.
