The structure of Korean sluicing-like constructions corresponds to that of the cleft constructions which contain no islands. In sluicing-like constructions, however, the negative island-sensitivity emerges clause-mately when the low wh-adjuncts such as ettehkhey ‘how’ appear with negation induced by island-violating movement in LF. The NPI or Neg is a scope limiting element which restricts wh-feature movement within its own scope. At this point, what gets the acceptability improved in such contexts is caused by the role of modality in C or discourse effects of the low wh-adjuncts. Modality in C or discourse effect of the low wh-adjuncts leads to immunity to syntactic constraints involved in intervention effects or negative island effects. The auxiliary verb can move to C across the interveners such as NPI or Neg. The wh-feature has a free ride prior to Spell-out and is checked against the uninterpretable wh-feature in C. The derivation is OK when the uninterpretable wh-feature in C is deleted by the Spec-head agreement. A tendency for a topic-marked phrase to override intervention effects or negative island effects lies in such a free ride. This argument is supported by the empirical data such as nun-marked low wh-adjuncts. This is the reason why the merger-type sluicing-like constructions are free from such effects.