* FridgeHorror: So, apparently everyone is matched according to genetic compatibility, rather than preference. This obviously means a person of the opposite sex. They have no choice in this, and it's permanent. What happens to homosexuals?
** They would probably choose to be Singles.
** Another example: The [[spoiler:red pill]]. The fact that it can cause the people who aren't immune to lose their [[spoiler:memories]] over the past twelve hours, which means that the Society [[spoiler:can basically make up any story and brainwash their citizens if they need to hide anything. Case in point: what actually happened to Matthew Markham]].
* {{Ship To Ship Combat}}: Team Xander vs. Team Ky, with Cassia/Ky being the OfficialCouple... in a book about how matching others is wrong, meaning...
** DoNotDoThisCoolThing
* StrangledByTheRedString: Ky and Cassia in the first book. Really, all that happens is that they run together and Ky teaches her how to write in old English. And they hardly speak of anything personal, yet they fall in love so easily...
* {{Tear Jerker}}: Grandfather's death.
** Also [[spoiler: Vick's sudden violent death]] in ''Crossed'', especially when [[spoiler: Ky]] carves that little fish for his gravesite.
* {{Iron Woobie}}: Ky.