Alain is mostly interested in Chiyo because she is part human, but more importantly, she's Makoto's niece. (He hasn't made the connection between himself and Chiyo yet. Kanon says that Chiyo has his nose.) Right now, she's mostly useful for getting Makoto back to the correct world.

Unfortunately for Alain, he doesn't realize that she takes after Makoto far more than she takes after Kanon in personality. He figures that Chiyo will just let him send her through a gate.

(Which results in a lot of yelling and Chiyo punching and kicking her father before getting out of there.)