From the introduction: The word ‘Yandere’ originated in anime fandom, and refers to a character who is crazy for someone (literally), often to the point of stalking, total obsession, and/or violence. This type of character is much older than the modern era, and is not unique to Japanese media. Examples can be found as far back as ancient Mesopotamian mythology, and there are a couple of DSM-5 entries that could fit the definition, so it has a basis in reality as well. Perhaps a bit exagerrated or romanticised, but still! Anyway, for the next 10 years, you’re going to have to deal with various yandere.