Modal concepts are typically expressed in the form of auxiliaries, adverbs, nouns, or adjectives. Despite the diversity, modal concepts were treated as black boxes, typically involving a necessity or a possibility operator. This paper develops a compositional account of Korean deontic modal expressions that are expressed in the form of a conditional construction. The morphosyntax of Korean permission and obligation opens up the possibility to break the black boxes and investigate the interior of deontic modal expressions. It is shown that we can derive deontic necessity from the compositional semantics of Korean obligation. However, the compositional semantics of Korean permission hints that permission has a distinct status from deontic possibility, which has been noted in the literature on deontic reduction.