Overview
Ahoge (アホ毛, "idiot hair") is sometimes used literally as a symbolic expression to indicate that a person is an idiot, but there are also cases where it is used purely as a character formulation, not necessarily in that sense.
In some cases, it is just a hair (or a bundle of hairs), but it is used as a sharp weapon, or it can represent the character's emotions (e.g., it turns upward when the character is happy, or softens when the character is sad).
When the hair exceeds a certain level, it is sometimes referred to as the main body.
The form itself has an old history, including the American cartoon character Betty Boop and Princess Sapphire, the main character in Princess Knight, and the name was born much later.
As a beauty industry term, it emerged as a youth term in the Kansai region around the 1980s and spread nationwide around the 1990s
Depending on its shape, it is given various common names such as antenna, antennae, horns, and so on. Ahoge is attached to illustrations of characters with it, regardless of gender, and is basically carried as a characteristic of the character.
Related Illustrations
Depending on the design, it may be attached to a few to most of the characters in the work.
In secondary works, it is sometimes omitted by the writer.
Whether it is intentional or just a mistake depends on the reason.