N4 — outside your level filter
Modifies a predicate directly and takes no copula, so there is no paradigm to conjugate.
そろそろ
sorosorosoon; about time toN4adverb
Related words
Readings and definitions from JMdict, © the Electronic Dictionary Research and Development Group (EDRDG), used under CC BY-SA 4.0; levels from the Tanos JLPT lists.