The complainant, whose identity is suppressed, gave tearful testimony before judge Michael Crosbie in the Dunedin District Court yesterday, where she detailed an ordeal she said lasted up to nine years.
The Dunedin man faces 14 charges which include a range of sexual allegations - indecent assaults, unlawful sexual connection and rapes - against two of his ex-partner's daughters.
The court heard the defendant and the girls' mother began seeing each other about a decade ago, during which the man would spend some nights at their family home.
A few years later he moved in semi-permanently, before moving out to a Mosgiel property in 2014, when things fell apart.
It is alleged during all times, the two girls were repeatedly sexually abused by him.
The allegations surfaced when the younger girl told a school friend, who pressed her to tell a teacher.
After initially denying she had suffered the same treatment, shortly afterwards her older sister claimed the same thing had happened to her.
A video interview the older complainant had made with police was played for the jury yesterday.
``It was the worst thing in the world. I hated it so much,'' she said of the alleged abuse.
She was asked to recall the first incident, which she estimated took place when she was about 8.
``I kept trying to push him away but I was only little,'' the girl said.
``I was scared and crying. I just wanted to go home.''
She alleged the offending progressed in severity as she got older and said she was even sexually abused in the bed the man shared with her mother when her mother was at work.
``He said: `I love making love to you' and I wouldn't say anything, I'd just cry,'' the girl told the police interviewer.
When asked how many times she had been raped she estimated it was upwards of 50 occasions and described incidents when they went camping.
In cross-examination, defence counsel John Westgate said the complainant had never raised the specific instances in previous statements.
``Are you calling me a liar?'' the girl asked.
``Yes,'' Mr Westgate said.
``Why would I sit here and lie about something like that? It's ridiculous. I'm not going to sit here and make something up,'' she said.
``This is why I didn't want to talk about this in the first place. I tried to tell my mum because I thought she would understand, but she didn't.''
Crown prosecutor Marie Grills said the woman had been readying the girls to spend the night at their stepfather's home in January 2015 when her reluctant older daughter said she had been inappropriately touched by him.
The younger daughter backed her sister and said the same had happened to her.
``It seems [the mother] chose not to believe the girls ... She was still in love with the defendant and wanted the relationship to resume,'' Ms Grills said.
Mr Westgate said his client's defence was simple.
``The defendant says these allegations are untrue, the girls are lying,'' he said.
The lawyer said he would highlight ``major inconsistencies'' in the complainants' stories and asked the jury not to focus on why the allegations arose.
The trial is expected conclude next week.
