The main goal of this paper is to investigate the pragmatic contributions of Korean GU. The data deals mainly with the cases where GU receiving high prosodic prominences co-occurs with gradable NPs, and the utterance marked by GU expresses speaker’s strong surprise. Thus far, many theories about the meaning of gu have centered on the analysis of its function as being non-emphatic (i.e., demonstrative gu ‘that’ and/or definite gu ‘the’). While it has sometimes been recognized that the interpretation of GU is emphatic occurring in an unexpected context, the exact nature of the semantico-pragmatic meaning has not been properly understood. In the present article, I propose a novel function of the emphatic GU by suggesting that the meaning of the emphatic GU is distinct from the non-emphatic gu: when GU co-occurs with noun phrases modified by adjectives, it functions as an emphatic marker and raises the unexpectedness effect. In this vein, GU plays a role as a scalar intensifier that contributes scalar implicature associated with the least likely end on the likelihood scale. Since the proposition with a low likelihood was out of the subject’s expectation, the speaker’s strong surprise arises. The implication of my findings is that the emphatic GU needs to be considered as a novel device for the focus marker implicating mirativity which intensifies speaker’s strong surprise at the low likelihood. (Korea University)