Kayako Saeki

 Born in 1963 (1971) to Nakagawa Kawamata, Kayako spent her childhood with her mother, who was an Itako (Japanese exorcist) who uses her daughter to "eat" the evil spirits she drives away from her patients. This marks the child for the rest of her life, making her a target for gossip and cruelty.
{When Kayako attends university, she meets Shunsuke Kobayashi, with whom she falls deeply in love. Years later, Kayako marries Takeo Saeki, the only person who understands and cares for her, and together, they have a son named Toshio on July 27, 1985 (28 January 1994). Kobayashi is revealed to have become Toshio's school teacher, and Kayako falls in love with him again. She writes of her feelings for him in the journal she kept.

Kayako instead falls in love with her Tokyo University professor, Peter Kirk, and begins passively stalking him; collecting items of his and obsessing about him in her journal.

One day, her husband, Takeo, who was already a very possessive and jealous man, finds and reads her diary, and becomes obsessed with the idea that Kayako was cheating on him with his son's teacher/her university professor - or worse; that Toshio could not be his son, but Kobayashi's. Driven by his anger and insecurities, when Kayako comes home that day, he violently attacks her. Kayako tries to run away but he pushes her to the floor and she sprains her ankle. Desperate, she starts crawling down the stairs, making it to the front door only to find Takeo slowly walking behind her. He then grabs her and snaps her neck to a 90 degree angle, crushing her throat and vocal cords which resulted in her only being able to emit a croaking sound as she screamed. Takeo then takes her to their bedroom and puts her in a trash bag.
Still alive, Takeo then grabs a utility knife and stabs her multiple times before gathering her up in the bag and puting her body in the far corner of the attic, through an attic door in the ceiling of their bedroom closet. After that, Takeo kills Toshio by drowning him in the bathtub, before also drowning his pet cat, Mar, in the same bathtub.

He then runs to Kobayashi's house, and kills Manami Kobayashi, Kobayashi's pregnant wife, putting her fetus in a sack for Kobayashi to find.
As he continues to fly into a fit of rage on the street, hitting the dead female fetus around in a sack, he falls on some garbage bags and is killed by Kayako; now an Onryo.
In The Grudge movies, it is implied that Takeo kills himself by hanging himself in his son's room, however it is later revealed that Kayako, now an Onryo, had ensnared and hung him using her hair.
Some time later, Kayako's body is found in the attic; Takeo's on the nearby street (in Toshio's room) and Toshio's in a closet.
Due to the rage of her husband, and her own dispair, Kayako became a prominant part of a Ju-on curse inflicted upon the house. From that day on, anyone who entered the house became tainted and eventually killed by the curse.