Relax guys, this story is like all the other "I summoned a demon/devil/creature and fell in love with her instead of being afraid, so I won her heart"
She's happy he did not flinch when he first saw her, and most likely experienced that pain in the past. I'm sure she's been summoned before (I first thought that the uncle had already, which is why he wanted him to stay out of the storage shed)...