This was such a cute story. Meeting online friends offline is usually a great time, so a story showing a proper relationship developing as a result is very enjoyable to read.
Plus, I like the fact that they were married in-game and voice chatting, which tells me they knew the other was a girl and were comfortable being married before meeting offline. They could have just done it for in-game benefits, but I like to think that was not the entire reason for it.
I also like how Yuzuki is showing proper restraint in doing more mature things towards Mio, but I think she can let it go as far as kissing without it becoming a moral issue. Though Mio is definitely testing Yuzuki's ability to hold herself back.