adverb, adverb taking the 'to' particle
rudely barging in; without hesitation; straightforwardly
Describes entering a place or situation boldly, often without invitation or regard for social norms. Carries a negative nuance of intrusiveness.
彼は人の家にずかずかと上がり込んだ。
He barged right into someone's house without permission.
ずかずかと近づいてきて、いきなり質問した。
He came straight up to me and suddenly asked a question.