Yandere (ヤンデレ), derived from the Japanese words " yanderu " (to be mentally ill) and " deredere " (lovey-dovey), describes a character archetype with an unhealthy love-related obsession that often results in violent outbreaks triggered by unrequited love or disappointment. Another similar type of character would be Yangire , who turns violent regardless of love.

Due to the controversial nature of Yandere as a trope in anime, often criticized of fetishizing or demonizing the mentally ill as well as romanticizing abuse, this aesthetic had to become distinct from the more wholesome Lovecore on a level beyond their aesthetic differences. Some mentally ill people choose to indulge in Yandere to find like-minded others and reclaim the concept as a form of (albeit somewhat unhealthy) coping mechanism.

In general, a Yandere is a character that is often depicted in a state of paraphilia (sexual perversion), manic depression, or codependence. The term is generally only used in reference to fiction, and does not hold any actual background in psychatric diagnosis. The sick, obsessive state of a Yandere is sometimes referred to as "darkening" (闇化) or "blackening" (黒化) in Japanese due to the shadow cast on the face of the character. Fans of the archetype like the extraordinary degree of obsession that a Yandere shows towards their darling.

However, the definition of Yandere is fluid and often has different meanings depending on the context. For example, on the Japanese website New Akiba , it is described as "a moe-type heroine that is suffering from a wicked heart", and in " Keitai Watch " it's described as "a character who seems to be mentally ill". It is sometimes pointed out that some of the attributes of a Yandere character are extreme exaggerations of real-life illnesses such as Borderline Personality Disorder (BPD) and Obsessive Love Disorder (OLD).

It is assumed that the term "Yandere" first started to spread among the mainstream media in 2005 because of the release of the visual novel "School Days" and the TV broadcast of the anime "Shuffle!". Shortly after that, Yandere has become a popular character archetype in various media. However, even before the term was coined, there were already multiple characters whose attributes would fit under Yandere. According to the Japanese website "Yandere Encyclopedia", the first instance of a Yandere character would be the 10 years old "loli"/underaged girl character Minatsu Tsukishima of the adult visual novel "Kurutta Kajitsu" from 1992. In order to monopolize the MC (main character), who is also her teacher, she starts killing all the women in his life one after another in gruesome ways in an attempt to make him commit suicide just so she can stay with his corpse forever. The use of the term "Yandere" then was popularized by NekoNeko Soft who used it describe the side character Sasai Yuuna, who appears in Chapter 3 of their visual novel "Gin'iro" from 2000.

Mathers Numakichi, the representative of the company Overflow which produced School Days, describes the Yandere boom as "a manifestation of wanting to seek more steadfastness and favor towards oneself". When asked regarding one of the heroines, Knoha Katsura, being labeled as Yandere, he answered, "I wasn't aiming for a Yandere character, so it was more of a lucky coincidence rather than something I 'created' on purpose". He also pointed out that the visual elements of the character were kind of mixed, and stated that "Both tsundere and yandere were a reflection of that time, people wanted to bring a person's inside to the outside".

In the late 2000s, the term "Yandere" also spread among the overseas anime community, and even western games started to incorporate this character archetype. However, the mainstream perception of the term in Japan is still mostly in a negative context, also fueled by multiple instances of murder cases by self-proclaimed "Yandere", such as Yuka Takaoka, who have been celebrated by fans of the genre.

The Yandere visual aesthetic is characterized by the juxtaposition of cute and disturbing imagery. Common visuals include edits of anime characters (like Yuno Gasai from Mirai Nikki ) that feature the iconic "yandere face"—often with shadowed eyes, an unsettling smile, and a deep blush, indicating psychological instability. These edits frequently overlay screencaps or fake text messages with pastel filters, heart motifs, and possessive or threatening text. Violence is heavily aestheticized: knives may be pink or heart-shaped, and blood is often stylized to fit the creepy-cute color palette of pink, red, and black. This has a strong overlap with the Japanese art movement "Eroguro" (erotic grotesque) and the related Gurokawa aesthetic.