This developmental research aims to (1) examine the design and developmental process, (2) investigate the nature and structure of the application, and (3) analyze the results of expert reviews and usability tests. Twenty-five participants, including a developer, an instructional designer, Korean language educators, educational technology researchers, human-computer interaction experts, and language learners, were involved in this study. This study was conducted in the following steps: (1) formulated design principles through the literature review of language instruction and learning theories, computer-assisted language learning, speech recognition technology, human-computer interaction, and scaffolding, (2) developed a functional software prototype that adopted the formulated design principles, (3) conducted expert reviews and learner usability tests, (4) revised and updated the application through the repetitive expert reviews and learner usability tests, (5) analyzed the results of the final expert review, usability test, and log data analysis, and (6) clarified the implications of the development research. The developed application shows an approach to addressing the challenges of second language classrooms that might cause a low-level of learner's language speaking performance. This study specifically delivers knowledge about the design and developmental process of computer-assisted language learning software. This provides guidelines for educational technology researchers and practitioners who work on similar projects.