、。
The days that followed flew by in a blur.
Literal
After-that [gen-の] days [topic-は], fly [like-ように] passed.
それからの日々 uses それから ('after that') + の as an attributive modifier on 日々 ('days') — 'the days (that came) after that.' 日々 is the reduplicated form of 日 ('day') used to mean 'every day, the days (in general).' 飛ぶように is the set expression 'like flying,' the Japanese counterpart to English 'in a flash / like lightning / in a blur.' A common narrative transition sentence.