Responses
That is because ri-in is cirrus's relative..., they are most probably cousins.. If you read correctly then you will remember, when cirrus lost candy and found her, he left candy to a boy, remember? That boy is ri-in's brother... And in cirrus's childhood back story, two kids were shown who with cirrus, thats ri-in and her brother.. they are cirrus's cousins
now that I think of it Chan-il's gf looks similar to Cirrus, not that I ship them but CI is pretty sus