In the teaching of singing, breathing control is an important component, the observation of which has conventionally required a teacher's long experience and refined perception. However, in online lessons where visual information is limited, there is the problem that physical differences are hard to perceive and it is difficult to obtain the information necessary to provide instruction. In this research, which uses a residual respiratory volume visualization system based on previous research, we verify the system's usefulness for supporting teaching, as well as implementing a new function to restrict inhalation volume, and evaluating the effects of this function. In the experiment, it was found that using the function that displays a gauge corresponding to the student's lung capacity and restricts the teacher's inhalation volume made it easier to control inhalation than when no gauge was displayed. When this function was used by music teachers, we confirmed that it was possible for the teachers to experience and understand the student's physical characteristics, and thus consider the physical difference before devising specific instruction methods. These results implied that the proposed system compensates for the lack of necessary information in online lessons and is useful as a tool to enable teachers to recognize the physical difference between themselves and their students.