ㄴ다구

Casual 'I'm telling you' or 'wait, really?'

-ㄴ다구 is the chatty spelling of -ㄴ다고, saying something again with force: 서로 예민할 때면 이런 거 가지고 싸운다구! 'when we're both on edge, we fight over stuff like this!' With a rising question mark it flips to checking what you just heard — 오 동욱이 형도 닭장 같이 간다구? 'wait, Dong Wook is going too?' There is no 요 on any of these lines, so they are all speech between friends.

Register: casual, no 요