The diffusion of smartphones has engaged people in communication using mobile messengers in everyday life. With the continued success of mobile messenger services, it is necessary to investigate what makes consumers to continue using it. Dr. Ae Ri Lee, Dr. Yong Wan Park (Barun ICT Research Center, Yonsei University), and Yuijn Park(Graduate School of Information, Yonsei University) conducted research on user satisfaction and commitment based on functional and emotional features of mobile messenger services. According to their research, users tend to express their emotions excessively and exaggeratedly because text messaging is limited in delivering the emotion exactly. This leads to a negative effect on user satisfaction and commitment. In addition, users feel fatigue when they have to respond to messages. On the other hand, an immediate response from friends could increase intimacy in communication. Since users feel connected, they continue communication and keep chat romos opened. The research results suggest that mobile messenger service providers should develop and improve the user interface for enhancing intimacy and reducing fatigue.