One trend you may have noticed over the last 10ish chapters is the characters saying "No no/no no no no nope!" a lot.
What does it mean exactly, and what's happening in the jp raws? It's exactly as you see it: they're saying the masculine form of いいえ/いえ which is いや… and いやいやいや...
Simply put, it's a versatile phrase which half acts as filler, and can also mean a lot of things.
In this manga, they're usually using it as an opening to comment on the current turn of events. Miyamoto uses it in this chapter to stall for time because he's trying to thank Foreman but also trying to do it in a way where he's not fully opening himself up at the start, but ends up doing so at the end of the chapter.
Here's a panel from chp.59 (Walking tour) when they're at the Gyoza place chugging beer after all of that walking.
They're doing it again. They're trying to call attention to the discomfort of downing all of that beer at once, but they don't need to say anything really because the situation speaks for itself.