Yeah, that is a bad end CG, haha. Unfortunately, there's a weird bug going on with Naninovel and Unity at the moment where sometimes the wrong background art loads when you load a save >.< It was reported last December by another dev, but so far no fixes for it cos the cause is unknown :(
You can fix it while playing by rewinding the text 1 line or by reloading the save again usually. But still, it's an extremely irritating bug, especially in this case where it's essentially showed you a major spoiler T_T I had it happen several times while testing, but it always loaded backgrounds I'd already seen at least. If it's loading stuff players haven't even encountered yet, then it makes it an even more major issue!
Glad you enjoyed the game though ^-^
(Edit: Also, whenever you see this, would you be able to edit your comment or mind if I delete it? Just in case anyone happens to come onto this page and accidentally see what you said since it's an ending spoiler x3)