When she was 12, Grace was abducted and then raped and beaten every day for 11 months.
So common are the practices of abduction, rape and forced marriage of girls in northern Tanzania that a single word is used to encapsulate them all: kupura. It is a word used by people from the Sukuma tribe to describe the snatching of girls in broad daylight as they walk to school; a three-syllabled euphemism that downplays their long-term physical and sexual abuse.
And yet here in the region of Shinyanga, the practice of kupura is validated by the oft-recited motto of Sukuma men: alcohol, meat and vagina.
"This slogan is in their blood and a way of life," says Revocatus Itendelebanya. "These are the three things they feel entitled to as men."
Itendelebanya, the legal and gender officer for the local NGO, Agape, says this sense of entitlement, in what is a perennially patriarchal society, also explains why passers-by don't intervene when they witness an abduction.
"When a Sukuma man is attracted to a girl he will start asking people where she lives, and what her routine is," explains Itendelebanya.
"Once he finds out these details he might wait for her near the borehole - or whatever he thinks is the best place to get that girl - and then grab her."
Kupura is so prevalent in the region that when a girl disappears, her parents will suspect what has happened. But rather than calling the police, they will seek the man out not to rescue their child, but to negotiate the dowry - or bride price - in cattle.
For daughters are sadly seen as a short-term investment for poor, rural households - cash cows that can boost a family's financial position at the expense of a girl's schooling and wellbeing.
Such is the value placed on a girl's head that Itendelebanya says parents will take their daughters to a witch-doctor if they are not attracting any suitors.
The ensuing samba ritual involves cutting cruciform nicks into the girl's chest and hands with a razor to not only help cleanse her of her bad luck, but to make her more attractive to older men.
And if ever there was a poster child to highlight the pernicious effects of child marriage, it's Grace Masanja.
"Bitterness still fills my heart when I look at them," she says, pointing at the cows grazing at the rear of her family's compound. For Grace they are a daily reminder of how she was treated like cattle, a commodity to be bought and sold.
"But given what I went through, I sometimes wish I had been born a cow," she whispers.
Her father had bartered a dozen cattle for his daughter but, despite daily beatings with sticks and her father's belt, she still refused to marry the older man.
But a deal had been made; a dowry had been paid.
And so it was that Grace was abducted on motorbike by her betrothed early one morning - all with the complicity of her father.
That night, and every day for the next 11 months, she was raped and beaten.
She was only 12.
"That day felt like the end of everything," Grace recalls, glancing again at the cattle.
A country of contradictions
When it comes to child marriage, Tanzania was until very recently a country of contradictions.
The 1971 Marriage Act set the minimum age of marriage for girls at 15 with parental consent - but a girl of 14 could wed where judicial approval was given.
And while the 2009 Child Act did not expressly outlaw child marriage, it did define a child as a person under the age of 18, stating that a parent should "protect the child from neglect, discrimination, violence, abuse, exposure to physical and moral hazards and oppression".