Animesexual, also known as Mangasexual, is a fictisexuality wherein one is romantically or sexually attracted to anime or manga characters. It does not need to be exclusive, although animesexual people may feel as though they are more frequently attracted to anime/manga characters than they are to people in real life. While it is normal to occasionally have a crush on fictional characters, if one is animesexual they might feel like it's more difficult/impossible to be attracted towards people in real life. This may also correspond to being a-spec, as some a-spec people might only feel attraction towards people who they could never possibly be in a relationship with, such as fictional characters.
The animesexual flag has an unknown creator. It is also unknown if the stripes have any specific meaning.
The term "animesexual" was most likely coined on a Tumblr blog. Anime/manga is a specific art style that originated from Japan. Therefore, "animesexual" implies attraction towards anime/manga characters.