hee hee--he's an optimist without realizing it--or rather, justifies it to himself by saying it's survival instinct to look for that angle of survival, and to look for it, one must assume it's there. Aerith is going to have a FIELD DAY when she discovers this about his way of thinking. FIELD DAY.
Sephiroth has no idea he's doomed, or that there's a reason why a Princess of Heart is, well, a Princess of Heart.
Honestly, it would not surprise me. All Dissidia!Seph needs is gliterly fingernail polish, he's so sparkly, and it wouldn't shock me to discover he HAD glittery fingernail polish on, we just can't see it through the gloves...and now this gives me images of Tohru managing to convince Seph to wear clear nail polish to protect his fingernails ("Because they can't be in good shape, under all that leather all the time!"), only the only clearish nail polish in the house is Aerith's glittery nail polish, and it'll be ok right, Mr. Sephiroth, since no one will see it...