Reibun
、。

As soon as they entered the shopping street, Hina started looking around wide-eyed like a country bumpkin visiting the big city.

Literal

Shopping-street [into-に] enter [when-と], Hina [topic-は] just-like country-visitor [like-のように] looking-around-[mimetic] surroundings [obj-を] looked-around.

おのぼりさん is a playful term for a 'country person visiting the city,' literally 'a person (who is) going up' — in Japanese geography, traveling 'up' (上る) means toward Tokyo/the capital. The さん adds affectionate politeness. まるで~のように ('exactly like, just as if') introduces a simile. キョロキョロ is the classic mimetic for darting eyes looking around in wonder or nervousness. The sentence captures a very specific Japanese cultural image — the wide-eyed rural visitor marveling at the big city.