This paper reports the results of monthly online lectures implemented in 2021 to complement a regular on-demand course. The complementary lectures aimed to further students’ understanding of regular-class content and secure interactive learning opportunities between instructors and students. In the lecture, instructors addressed and explained difficult questions from the coursebook and answered students’ questions. Although we started with live online lessons in the first semester and high participation was observed, the number of participants decreased over time. Therefore, in addition to these lectures, we recorded learning-support videos in the second semester and broadcast them on the learning management system at our university, allowing all students to access them anytime from anywhere. Consequently, numerous students watched and made use of them in language learning. These complementary lectures seemed to assist students with their chances of relearning and interacting among themselves. Future research is required to conduct complementary classes by incorporating collaborative learning with a break-out function, targeting students’ proficiency levels and collecting participants’ responses.