
They are invisible - nothing like being attacked by a monster you can't see in daylight. Final Fantasy: The Spirits Within, the phantoms began rising from the shore and started killing unsuspecting people playing about in the beach one afternoon.In episode 6, the creatures surprise everyone by attacking in the middle of the day, when Saya's friends are around. This makes it easy for the protagonist to compartmentalize, playing the part of Ordinary High-School Student by day, and slaying monsters by night.

Blood-C has nocturnal monsters called elder bairns that feed on humans after dark.Titans are pretty damn scary no matter what time of the day they happen to be eating you. This makes the attack on Castle Utgard at night all the more shocking. So it is on clear, sunny days that we are able to see hordes of Titans devour humans alive. Justified in Attack on Titan with the Titans, which appear to harness most of their energy from solar radiation and slow down and eventually stop moving when out of sunlight.Sunshine Noir is another example of a traditionally night-based genre being set in the daytime. See also Weakened by the Light and Scenery Dissonance. Not to be confused with Light Is Not Good (although it can invoke this), or the horror video game Daylight. Not only are the monsters after you, the most basic of tropes has failed. The point is: you're screwed and you have nowhere to hide. In fact the zombies are more likely to appear during the day because the purpose of their stories is often to show the crumbling of civilisation which is better showcased when the picture consists of ruined buildings and empty urban areas when they are supposed to be overpopulated. The Zombie Apocalypse around the corner doesn't care if it's nice out and you've decided to go sunbathing.

The Eldritch Abomination decides to rise on a sunny day.
ELDRITCH ACADEMY GROUNDS SERIAL
The Ax-Crazy serial killer suddenly shows up at your home when all of the lights are on.

Whatever the reason may be, we get scenes of frightening imagery in broad daylight or well-lit rooms.
