Yakudatazu Skill ni Jinsei wo Sosogikomi 25-nen, Imasara Saikyou no Boukentan Midori Kashi no Akira - Vol. 6 Ch. 29.1 - A New Threat

[MangaDex]

 

[rexmundi]

Mutated hippo

 

[StLOrca]

Like they aren’t already two-ton murder machines.

 

[Madologist]

These aren't mutated hippos or special magic monsters.
These are just your regular hippos.

 

[alacaelum]

All of this because a whiney little shit is salty because his status as a privileged family boy didn't buy his advancement in the adventuring lifestyle.

 

[Otherworlder]

All hippos are gregarious, long-jumping, rage hippos. These aren't special. Fun fact: hippos can't swim. They move through the water by jumping off of the bottom. They do so so well and so fast that they're moving through even fast rivers faster than a lot of critters can swim, and faster than more than a few can even run on land.

I rather suspect that this fiery girl is the toddler that the MC saved at the cost of his hand many moons ago. She asked about his injury a few chapters ago, a chapter that isn't in Mangadex because reasons. It looks like she's made a career out of paying it forward.