^Yeah I met way too much "lesbians aren't real, they are just playing, and will become normal when they will take a D" in real life to "take it less seriously ".
It does look like they are looking at a third (probably male) person but I'll just pretent they look into a mirror and Frieren is a bit too into whatever thing they are trying together.
imo the third person is in a "third wheel" kind of position. You see, Fern looked quite annoyed at the third person in the picture, like, "why are you still here? can't you read the room and get out of here so we can have some fun?"
^In one word: No Much later in the WN: There may be a side character that is nursing a hopeless unrequited crush on another side character. But even that may be a reach.
^Agreed. Unless there is an obvious indication that there is a third person, I'll give the artist the benefit of the doubt that they're simply drawing the characters without putting much thought into composition.
The "third person" is the audience, not a real person. That's how these comps nearly always work. I definitely wouldn't assume some guy, even without knowing the artist draws pretty much only women.