@Sippers
What was so dramatic about that last part??
Fukatsu can't recognize people's faces, so he lacks empathy for them, since everyone looks the same to him.
He had interest in Gokigen and his brother because they seemed different from every other egg he'd seen so far, but once they turned into "normal" eggs, they lost all the value to him.
The shock here is how easily Fukatsu is willing to part ways with someone if he can't find a superficial trait that allows him to identify that person.
When his sister asked him what he'd plan to do if Tomose turned into a normal egg, just like Gokigen and his brother, Fukatsu didn't stand his ground and defend his friendship with her, meaning his relationship with her is just as shallow as his was with Gokigen.
That's sad when you consider how easily he let go of his father running away, and that he might just do the same if it were to happen to Tomose.