I'm going to have to investigate exactly what they're saying there in the third panel...

Paracite said:

I'm going to have to investigate exactly what they're saying there in the third panel...

For my knowledge and all it's worth, it's about how he is feeling chilly lately and Kirishima replies with that's what he gets for dressing so lightly.

But well, I have to say (after consulting some native Japanese), this one is hard that even the Japanese aren't all able to understand (certainly not my bosses). No wonder Kongou is speechless.

Aha! It's Shimokita-ben. Which makes sense, being as that's where Oominato is.

Of course, to get the nuances of using a relatively obscure dialect like that is basically going full Scots or understandable Appalachian.

こごん is derived from ここの, where the contraction of the /no/ > /n/ creates a voicing in the previous ko (/ko/ > /go/), a feature that occurs in various dialects.

わんづか is すこし

さんび is 寒い (though you can guess that one pretty easily)

Hence ここの所の朝は少し寒いの。

なんぼ is the same meaning as いくら、but I'm not 100% sure on what the きや in 厚着したきや　maps to.

(Gave it a shot)

Kirishima's hidden accent?

lol i completely looks like Kongou when first reading it