Born to first-generation immigrants from Samoa and Ethiopia, the 26-year-old grew up in the outskirts of Los Angeles but later moved to Bozeman, Montana, when he went to college.
It was there that he fell in love with the outdoors and the spectacular ice climbing opportunities Montana has to offer.
Ainuu taught himself how to climb and is now a seasoned professional, embarking on trips across the United States
But he says living in a predominately White area, whilst taking part in a sport with few other Black athletes, weighs heavily on him.
Despite not recalling any overtly racist incidents, the climber says it is more an accumulation of "microaggressions" from both the local and climbing community, such as people commentating on his dreadlocks.
"Most people are like 'Oh, it's a compliment, it's kindness,' but what it happens to be is kind of backhanded," Ainuu tells CNN Sport. "They're seeing that you're different and feel like they have to say something about it.
"I'm pretty mellow, so I just ignore a lot of stuff. If someone says some stupid racist thing, I'm like: 'Whatever, I've heard this before.'
"But it really does weigh down on you. It all builds up and whether a person handles that by bottling it up or ignoring it, there's still an effect."
With films such as free solo making it into the mainstream and with climbing gyms on the rise, the sport has witnessed a boom in recent years.
But the cost of clothing and safety equipment acts as a huge barrier to entry for many and the lack of representation amongst the world's top professionals is being recognized more than ever before.
Now a member of The North Face's elite climbing team, Ainuu wants to change the narrative around outdoor adventure sports.
"I don't really like being in the spotlight, having all this attention brought to me, but what I've realized is [...] there are so many people that are looking up to me [...] and all these other Black and African-American climbers or athletes or musicians," he says.
"Just seeing someone that looks like you, doing something and excelling at it is extremely empowering."
It's why Ainuu was so excited to be part of a new documentary film called "Black ice which looks at a collaboration with Memphis rox -- a not-for-profit climbing gym in South Memphis, US.
The center provides a safe haven for people away from the streets; a place to relax and dive into a sport that may at first seem unfamiliar. No one is turned away, regardless of their ability to pay.
Through its inclusivity and caring ethos, the organization has opened up the world of climbing to the local community which suffers from poverty and a lack of opportunity, especially in Black communities.
Elena Delavega, Associate Professor at the University of Memphis, tells CNN Sport that South Memphis is one of the poorest areas of the city which is "underserved and under-resourced."
She also says the area is under threat from encroaching gentrification.
"That is a problem for this neighborhood because there is a desire to remove the traditional residents and to 'improve' the area," she says.
"But no improvements are happening while poor people live there."
According to the 2020 Memphis Poverty fact sheet, the poverty rate for the city is 21.7%, with the percentage higher among minority groups.
The "Black Ice" film documents how members of the gym's staff, many of whom had never been ice climbing before, travel to Montana where they met with Ainuu, fellow ice climber Fred Campbell and climbing legend Conrad Anker.
Learning from the experts, the Memphis Rox team spend time scaling frozen waterfalls and skiing in some of the coldest temperatures they've experienced.
"It was super cool. I mean, just having that much melanin in Montana," Ainuu laughs.