Put Simply, Mahotsuka-chan used "Enchantment" ..... "IT'S SUPER-EFFECTIVE!"
It also seems that the book author (H. Fujiwara) is either (1) a closet pervert, or (2) a visionary who prepared said book and it's ... er, contents, to function as a wing-man for these two to become a couple.
Also, IN-teresting that this library seems to have no CCTV Security System in it, otherwise, anyone on the opposite end would likely have seen "that which perhaps should not be seen".
In The End, this conclusion works: "Well Isn't That Cute? ... BUT IT'S RIGHT!"