User blog comment:IamJakuhoRaikoben/Chapter 450: Alone in all the World, Review./@comment-5894890-20150831164039/@comment-1359322-20150901011624

Zeref has live his life 400+ years with almost little interaction and avoids people because he can't get close to them. Same goes with Mavis, she spent 1 year avoiding contact with anyone. We may feel that it's rushed but for those two who can't die and can only take lives, just having 1 person in the same situation may be more than 1 can understand.