Other paintings he shows us have themes of memories, childhood, racism, street art, his background, and hope. His works are rough, messy, highly textured, but compelling and intensely coloured.
A triptych of rich colours represents how he felt as a child after he'd "had the bash", he says.
"Somewhere I'd see these beautiful colours, and what happened to me didn't seem so important."
These works and others form Sebastian's first exhibition, Living The Dream, which opened at Wanganui Community Arts Centre last night.
Sebastian is a third-year Bachelor of Fine Arts student at Whanganui UCOL, and has come a long way from his childhood on the wrong side of the tracks.
He grew up in a notorious Tauranga gang family, which he describes as being "the real-life Once Were Warriors".
"I grew up with a lot of abuse and violence in my family, I went through lots of different foster homes and schools, and some of my family are full-on gang members."
Sebastian, who has links to Te Puke-based iwi Tapuika, may have ended up on that path as well, had it not been for his love of art.
"I used to see my dad drawing taniwha, but he was just doodling. I asked him to teach me how to draw. I was always drawing when I was a kid, but I never took it that seriously."
School art teachers told him he had real artistic talent, but a constantly transient lifestyle meant none of these teachers were able to help him for long.
In his early twenties living in Tauranga, unemployed, and with no real purpose, Sebastian was looking for a job when he heard about the foundation art course at Whanganui UCOL.
"Art was my childhood dream, it was my place of freedom, but all the violence I was surrounded by had made me forget about that dream. When I heard about that foundation course, I knew I had to do it."
He arrived in Wanganui wanting to learn more about art but lacking in confidence and not sure if he had any true talent. "When I arrived in Wanganui, I had this feeling of deja vu. It felt like a second home, and it still feels that way."
To his delight, he graduated top of his class and later enrolled in a Bachelor of Fine Arts.
Two years of studying have taken some getting used to: "It's taken me out of my comfort zone, that's for sure."
Sebastian has very little money for art supplies, but he's not fussy. He'll use the left-over paint belonging to his fellow students or his tutors, he'll use paper out of the recycling bin, and he's even learned to make his own canvases.
"You don't need to have flash supplies to make art, you can use anything."
He does admit to a weakness for oil paints and oil sticks because of the intense, rich colour they provide.
Sebastian is excited and nervous about the start of his first solo exhibition.
"They're really personal works, and a whole lot of strangers will be looking at them."
He thinks it's unlikely his family will make the trip from Tauranga to see the exhibition. Most of them are glad I'm doing art but it's taken them a while to get used to the idea."
One of his "hard-core gang" cousins is the most supportive of his artistic endeavours and has encouraged him to keep following his dream. One of his nephews is also interested in art and wants to be just like his uncle when he grows up.
It's children like his nephew that Sebastian wants to help once he graduates from UCOL.
"I really want to help troubled kids, and I want to use art to do it. There are so many troubled kids, and they don't have a chance.
"I want to give them a chance, and I know I can do it, because I've experienced what they have."
While he's been in Wanganui, Sebastian has found himself a group of mentors - experienced artists who have been touched by his story and impressed by his art. His mentors have paid for his exhibition, helped him with art supplies, and give him advice and support.
Among those mentors is printmaker Julia Ellery, who met Sebastian when he visited one of Julia's exhibitions with a fellow student.
The two got talking, and Sebastian expressed interest in holding his own exhibition.
"We're always on the look-out for different, new artists. I was impressed with Sebastian's work and his story, and I wanted to help him."
Julia said she enjoys Sebastian's art because he uses it to "make sense of his life".
"He is telling his life story through his art."
She is looking forward to seeing what the future holds for her protege.
"It's up to Sebastian whether he evolves or not. We can mentor, but he has to do the work."