* {{Moe}}: Yukino and Shun's little sister Saemi.
* TearJerker:
** Yukino's backstory. She is one of the oldest and most powerful Gate Keepers. Sadly, using her gate ability so often has made her apparently [[WhoWantsToLiveForever ageless]]. Not only that but for an unknown number of years she'd been trapped in some kind of icy realm, until Shun found and freed her. Then 31 years later she's killed in a battle with the entity called the Ghost Girl.
** Shun's backstory isn't much better. He grew up despising his father for seemingly abandoning his family, only to learn that his father was a Gate Keeper like him, and had died in an accident.
* TheyWastedAPerfectlyGoodCharacter: Francine, a main character from the Gatekeeper games, was AdaptedOut of the anime, thus losing any chance to expand on her character in the anime adaptation.