Lizzie Doss

Lizzie is the female lead of Crimson Gray and a deconstruction of the yandere archetype.

Personality
Lizzie has a severe mental condition that leaves her sociopathic toward the majority of humanity and gives her a desire for a specific person to direct her full attention towards. Though she watched several people, the person she focused on was John Nichols. When he reciprocated her feelings, she became more obsessed with him, but at his insistence also more balanced, developing interests of her own.

Aside from this, Lizzie appears to be somewhat of a romantic, wanting things like a traditional wedding. She also has some normal opinions for a girl her age, for example having read that talking about marriage would "scare off boys" (she doesn't see the irony in saying this to someone she kidnapped).

Lizzie's primary weapon is an axe, but she also uses knives and appears to enjoy collecting them. Her favorite subject is chemistry, where she learned to make chloroform. Aside from John, she appears to have few interests that are not practical, completely uninterested in music or movies.

Childhood
In approximately 1972, Lizzie's mother participated in a KoiTec experiment while pregnant with Lizzie, irrevocably altering her psychology and physiology. It's impossible to know how much of her later personality was nature and how much was nurture, but she had both a dysfunctional family (absentee father, addict mother) and signs that she was unusual from a young age.

When Lizzie was "very young" she helped her abusive mother overdose on unknown drugs, intentionally killing her. In elementary school, she killed a girl who was cruel to her, making it look like an accident. In middle school, Lizzie tried to keep to herself, but said this attracted attention from other girls. By high school, she appears to have learned to act more normal, finding a girl to pretend to be friends with.

Crimson Gray
In 1990, her last year of high school, Lizzie fixated on John. In the canon path, they started dating, but when John refused to sleep with Lizzie, she kidnapped him and held him in her basement over a week-long vacation. John escaped his bonds but remained as a show of trust in Lizzie, which deepened their relationship.

Unfortunately, they had attracted the attention of KoiTec, which captured John to use him against Lizzie. With assistance from John, Lizzie was able to kill all the KoiTec operatives and free him, then cover up the incident and escape.

Dusk and Dawn
In 1992, Lizzie was enrolled in university along with John. It was unclear what she studied, but it was implied that she wanted to receive a Bachelor's degree in under four years (since it was an American university). Lizzie had delayed marriage due to fear of KoiTec finding them, though these fears are implied to be irrational.

In the canon path, she and John are married in a private ceremony. They seem to go through college without making any serious connections, so there is no one to attend the wedding.

Crimson Gray 2
Though the existence of a sequel is uncertain, Sierra has stated that it would take place in 1995 and focus on Lizzie and John after their marriage. According to Steam comments, it would further develop the relationship between the two main characters, deal with social and corporate subplots, and address yandere pregnancy in a way different from other stories.

The Future
Sierra has stated that John and Lizzie have two children together, both of whom inherit Lizzie's condition, but in different ways.

Crimson Gray ends with an epilogue an unknown number of years later that suggest they lived long and happy lives together.

Trivia

 * Lizzie's name is probably a reference to Lizzie Borden. Supporting evidence includes both using an axe as a weapon and their mothers being named some form of "Abby." Her last name could be a reference to serial husband murderer Nannie Doss.