@Rose2Blossom
I'd never heard of Line before myself, so I had to do a little bit of research. While it certainly does sound better than Skype, I'm not sure - based on some quick looking around - that it really stacks up against Discord for chatty business... at least for me, anyhow.
It seems like Line's main focus is phones - since it apparently requires a phone number, or Facebook account to use - while Discord has no such requirement. For myself, my main focus when it comes to chat apps is always going to be my Desktop PC, so I generally prefer to see developers focus primarily on those platforms - whereas Line, as an entire corporation, seems to place emphasis on the phone market. While there's nothing wrong with that in and of itself, and it probably makes sense for their target audience, it does somewhat give me pause.
With that said, I suppose the largest barrier to being overly interested in it for me is the fact that everyone I know has already switched from Skype to Discord, and seems quite happy with both the desktop and mobile clients.