Dusk Maiden of Amnesia/Nightmare Fuel


 * Nightmare Fuel and Tear Jerker: The manga opens with the shadowy image of a crying girl and a tale of a girl being sacrificed to protect the school. Now consider that we learn Yuuko was not only sealed in that underground space, but that she also had a broken leg. She died slowly and in pain, scared and alone in the dark, tearfully pleading for help.
 * Episode 4 of the anime gives us our first proper look at Shadow Yuuko as she stands over a sleeping Kirie, displaying a full on Slasher Smile full of dagger-like teeth.
 * Episode 6: Kirishima Yuuko being offered up as a sacrifice for the fictitious monster that she created as part of a Batman Gambit that had Gone Horribly Right. People she thought of as friends were willing to kill her to save their own skin, and the worst part is, there wasn't even any malice towards her when they were going to do it.
 * Episode 5 of the anime, while mostly lighthearted fun, has a really dark Mind Rape-ish segment that feels more in line of Puella Magi Madoka Magica or a Shadow confrontation from the Persona games.
 * Oh hi Episode 6. Nice of you to bring back the Human Sacrifice, Murder and Darkess into the anime. Jeez.