I was going to agree with you since hobby, for me, is more of a solitary activity. But then I do know several people at work who would say soccer or basketball

I was going to agree with you since hobby, for me, is more of a solitary activity. But then I do know several people at work who would say soccer or basketball is their hobby, something they play regularly and look forward to doing. Although kendo sounds like it would be difficult to keep up outside of school. But I have not lived in Japan to know how popular it is outside of school.