Evolved kappa. It only eats the flesh of obese men. It sits at the bottom of the sewer until an appropriate prey presents itself. It smiles when hit on the head.
Despite being the Water Tiger, this creature is Fire-based. That means that not only is Yuri's best fusion choice Man Dragon, but also that Margarete's Grenade does twice the damage it does to the regular Kappa. This battle is much easier than the enemy's HP denotes.
The Water Tiger, "Shuǐ hǔ", is a creature from Chinese myth analogous to the Kappa of Japanese legend.
Much like the Kappa, it is said to live near lakes, rivers and other bodies of water, attempting to drown nearby humans who ventured too close to the waters edge.
Unlike the Kappa, however, it had a more feline head, which would poke above the water, and was regarded as much more vicious and aggressive than its Kappa cousins.