Could be nostalgia or deja vu. Or in any case for the sake of the situation being funny
Then I accept the latter, even as parallel world genderswapped Rin, he can never really take a break from Einzbern,Herk,Emiya combo...
You're a pervert, bro!That's why, I can't do it with someone I don't like!Why?Huh? What are you saying...NOOOOOOO! DON'T COME!This is bad! He's after you!Now! Illya-san, run away! hurry!CafeteriaWait up!What's happening actually?"Mana transfer" with a boy is impossible!If you get caught, he'll do this and that to you!