This paper reports on the development and operation of the English as a Common Language (CELF) tutor service at Tamagawa University in Japan. The authors explain how this service was established to support students' English learning through individual tutoring, multilingual exchange, and self-study opportunities. This paper outlines the program structure, tutor roles, scheduling system, and the types of academic support provided, including presentation practice, TOEIC preparation, grammar support, and speaking support. Furthermore, it examines student usage patterns and the educational value of the tutor service within the framework of the English as a Common Language (ELF) curriculum.