Myriad Colors Phantom World: The Polka Dot Miracle (OVA)

The OVA opens with Haruhiko explaining human vision, optical illusions, and visual preconceptions to his classmates at Hosea Academy. During their summer trip by the sea, they're tasked with exterminating a Phantom that's been scaring visitors away, in exchange for free lodging and food. The Phantom's behavior is initially a mystery, but it eventually appears and uses its ability to manipulate light and temperature to create a polka dot censor, making the girls appear naked.

The boys struggle to resist the illusion, but Haruhiko manages to repel it for a moment with the help of his summoned spirits. However, the Phantom adapts and creates a more convincing illusion, causing the boys to give in to temptation. Haruhiko and his friends eventually develop a strategy to counter the Phantom's ability, using a combination of fire and Albrecht's powers to dispel the illusion.