User blog comment:FairyRaven/Fairy Tail Chapter 448: Fight the Power! Review and Commentary/@comment-114.79.32.226-20150817072920/@comment-7418318-20150817093410

I really can't imagine there being any romance between them.

For starters, Zeref was still affected by his curse, so them getting closer than a few meters to each other would have been risking Mavis' death...

Not to mention that he's over 400 years old while she's 12 or a little older.