User blog comment:Miskos3/Fairy Tail 525: Why Did the Emperor Never Love His Child?, Review/@comment-5303512-20170304145630/@comment-7418318-20170304230906

The point of our argument is that Misk says it is entirely possible and not out of place for them to have naturally conceived Larcade off panel and I say it is unlikely in the extreme.

I mean just look at the flow of the scene: http://mangafox.me/manga/fairy_tail/v53/c450/16.html

Mavis encourages Zeref not to give up, they both break out in tears hug and then kiss... and the moment their lips meet, the scene goes black and you see the trees in the background dying. Where is there any room to insert an off-panel sex scene in that?

Do you think they start crying, then have sex, then start to cry again and share their final kiss? Or are they supposed to have sex between Zeref saying that the world rejects him and Mavis tells him not to give up? Or maybe during him telling Mavis about his nation?

The entire scene from start to finish has a nice and logical flow with no room to fiddle anything in between in my opinion. So if IF it turns out they had sex during that scene, it will be a retcon to me.