He paid for oral sex but then had intercourse with her without consent, and when she repeatedly asked him to stop, he punched her around the face until she lost consciousness.
When Maru eventually left, he stole the woman's phone, an act Justice Peter Churchman said seemed to be deliberate, to stop her calling for help.
The victim slipped in and out of consciousness for the next 24 hours and was only found when police officers were sent to her home for a welfare check.
In her victim impact statement, the woman said she was now scared to leave the house, use public transport, or be left alone with men.
Injuries to her face, eyes, and nose were so severe that she couldn't lie down on her back. She said she had difficulty remembering even small things.
"I am scared of men. This has affected me so that I cannot work anymore.
"I live like a hermit, I don't go anywhere, I see no one.
"My counsellor is currently assessing me for PTSD, and to what degree of counselling I need.
"I am now in financial hardship because of this. I cannot catch public transport because of my fears.
"It has affected my existing mental health issues, and it makes me want to use drugs and alcohol. But that doesn't even help.
"I want this to end. I want me back again. To be back to the way that I was."
Justice Churchman had to pause the sentencing twice when Maru interrupted proceedings, once by taking off his shirt while in the dock, and a second time for interacting with family members in the public gallery.
Justice Churchman noted that Maru was young and so was likely to be more impulsive than an older person.
But he said that the seriousness of the offending, and an assessment he had a high likelihood of reoffending, required a strong sentence.
Maru's lawyer Steve Gill said Maru still rejected the jury's verdict that the sexual intercourse was rape, but that he admitted responsibility for the violent attack.
Do you need help?
If it's an emergency and you feel that you or someone else is at risk, call 111.
If you've ever experienced sexual assault or abuse and need to talk to someone call the confidential crisis helpline on: 0800 227 233 (08002B SAFE).
Alternatively contact your local police station - click here for a list.
If you have been abused, remember it's not your fault.
