In requirement engineering, an important issue is how to transform and tailor the informal system requirements of users or customers into more structured specification documents, which are then used by the software developers. In addition, it is both challenging and necessary to redefine and analyze, from ill-defined or unknown requirements, specifications correctly and automatically generate test cases with them. There are few kinds of research in Korea for automatically reducing requirement complexity and developing test cases of the Korean language-based requirement specifications. Why do we need requirement simplification? Requirement complexity causes analyzers less readability and low understandability. To do this, we propose the automatic cause-effect generation via a requirement simplification mechanism of informal requirement specifications with the Korean language, which works the following procedures: (1) the automatic simplification of informal requirement sentences, (2) the generation of Condition/Conjunction/Clause Tree (C3Tree) Model, (3) and the Cause-effect generation.