Shidaidaka
Shidaidaka (次第高) is a yōkai reported in Shimane Prefecture and the Chūgoku region of Japan that grows taller and taller the longer a person looks up at it, looming ever higher over the viewer. The folk remedy is to look at it between one's legs, which either reveals it as small and harmless or makes it vanish. It is a classic yōkai that preys on human perception.