Sengoku, Nadeko

Nadeko, a main character of the Monogatari Series, has been Tsukihi's friend since elementary school. She wears a waist pouch, casts her eyes downward, has bangs covering her eyes, has a shy personality, and can be easily amused. Koyomi played with her a lot whenever she visited his house after being invited by his sisters. She refers to Koyomi as Koyomi onii-chan and appears to have feelings for him.

Nadeko Snake Arc

[Spoiler] She was cursed two times by a classmate who liked the boy she rejected, and the rejected boy. While the first one had been banished, Koyomi is forced to battle the second to keep it from killing Nadeko. [/Spoiler]

She's quite protective of her hair (particularly her forelocks) thinking that it's her place to guard more than her panties. When she finally combed her forelocks aside in Nisemonogatari, Koyomi commented that she has a glare just like a serpent, foreshadowing the story of Nadeko Medusa.

Nadeko Medusa Arc

[Spoiler] Nadeko reveals her true colors: an obsessive, egotistical, manipulative and cynical girl who because of her unrequited love had resorted to becoming a destructive deity enshrined as a god in North Shirahebi Shrine. Her immaturity of thought gave her the desire to kill Araragi, the object of her unrequited love. The arc was revealed as a decoy made by Nadeko herself to push to blame of turning into an oddity onto a scapegoat of a wristband she called "Kuchinawa", maintaining her act of being the victim. Her obsession with her forelocks was also shown to be an allusion of how she hides her true self by appearing as a hapless and cute girl.

Eventually, Kaiki resolves the situation by reminding Nadeko that her identity is not fully defined by her unrequited love, and that become a mangaka, one of the dreams or hopes of Nadeko revealed in this arc, is also a reason for Nadeko to move on past her unrequited love and to move on with life. Nadeko complied. [/Spoiler]

Koyomi Reverse Arc

[Spoiler] Nadeko is an "ex-god" in North Shirahebi Shrine as Mayoi Hachikuji has been enshrined. She speaks like a tomboy, drinks copious amounts of alcohol and has rude mannerism in this arc, confirming the boyish and brattish side of Nadeko as a part of her real personality. It is also revealed that Nadeko had regretted this part of herself. [/Spoiler]