This is from the recent FGO Xmas event. Included in the twitter post:
Enkidu: "My poor friend... but now that I've heard your story, perhaps you've mixed up Christmas with Valentine's Day? (The same thing will probably happen then. But he doesn't need to hear that.)"
Hahaha, he seems so embarrassed (or in despair, either way..).
Context is that in the F/GO Christmas event, Gil was waiting for Santa Alter to come and give him presents and then was going to say, "My present shall be you!" Santa Alter was near, heard that, and decided to just leave without giving him anything, that and probably because he was in the naughty list.