LONDON, Ontario -- At first blush, Hayden Foulon's bedroom looks like a shrine to Mitchell Marner.

A blue-and-white Marner Toronto Maple Leafs jersey dangles on the wall above her bed. It is secured there by a hockey stick autographed by the forward and his Maple Leafs teammates.

A canvas with Marner's photo sits in the corner with a personalized message that reads: "To Hayden! Happy 6th Birthday! Your friend! Mitch Marner."

"I love Mitch," Hayden, 6, said. "I miss him."

As Hayden is showing a visitor her room, a dog runs in and begins licking her.

"What's the puppy's name?" she is asked.

"Mitch," she replies, flashing her gap-toothed grin.

Of course it is.

Hayden beams whenever she hears Marner's name. His impact reaches all the way down to her heart, a beacon of hope in a young life that has experienced far too much pain.

Hayden has battled acute lymphoblastic leukemia for almost five years. She was first diagnosed when she was 22 months old. Her mother Lindsay estimates her daughter has spent almost a year of her life in various hospitals in London, Ontario, Toronto and Philadelphia.

Hayden was declared cancer-free in the spring. Or so everyone thought. A follow-up test in July revealed a number of cancerous cells. And with that, Hayden's battle continues.

"She is my hero," Marner said, his eyes welling up. "What she has gone through and the way she has fought in her brief life is an inspiration for all of us. All I want to do is to try to bring some happiness to her life any way I can."

Their blossoming friendship has tugged on the heartstrings of the Foulon family.

"Him making a big deal out of her has made her happy," said Hayden's mother, Lindsay. "And I will always be grateful for that. Nothing is more important than whatever happiness she can have.

"With her being in the hospital for such a long time, she doesn't have the opportunity to go to school and make friends. She doesn't get to be a normal kid. Just by him saying she's his friend, he's acknowledging her. That makes her feel important. And it's given her a lot of strength and a lot of courage.

"She's on cloud nine when we talk to her about him. Seeing her light up makes the crummy days feel less crummy. When she smiles, we smile. We take the good and the bad. And unfortunately, there have been some bad days.

"The things Mitch has done for her have made her the happiest kid."

Video: Mitch Marner super fan Hayden Foulon says hello

Hayden first met Marner, then a forward for London of the Ontario Hockey League, when he toured the Children's Hospital at London Health Sciences Centre in 2015 with teammate and current Arizona Coyotes forward Christian Dvorak.

"Dvorak and I, that was kind of our thing," Marner said. "We'd go there and walk around. It's the OHL, but you still have the spotlight in London to be able to change someone's life. It was our goal just to make the kids feel better and forget where they were."

In Hayden's case, it meant making a new friend. And vice versa.

When Marner, who wears No. 16, joined the Maple Leafs, Hayden would watch him on TV. While in Toronto receiving treatments in the spring of 2017, she'd run up to the screen, point at Marner and yell out, "Go Mitch One-Six!"

"She still does that," Lindsay said.

Video: Foulon awaits Marner for a fist bump prior to game

Mitch One-Six sent Hayden the autographed canvas for her birthday March 2, then invited the Foulson family to the Marner Assist Fund charity event in the Toronto-area community of Vaughan in August. The goal of the Marner Assist Fund is to create sustainable change for children and youth by providing resources that will make a significant impact on their futures.

"He was incredible," Lindsay said. "He arranged for a fire truck -- a real full-sized one -- to be there for her. They took lots of photos."

Marner's father, Paul, who helped organize the event, offered to send Hayden to Walt Disney World via the Marner Assist Fund. Lindsay suggested Hayden's real thrill would be to go to a Maple Leafs game, which they did for the home opener against the Montreal Canadiens on Oct. 3.

"Having her down at the opening game was amazing," Mitchell Marner said. "Just the smile on her face … it meant so much. It was a life-changing experience for both of us. Just want to make every moment last, and make sure she enjoys it. We've grown very close in past years."

November is Hockey Fights Cancer month in the NHL, though the movement is a year-long cause. Mitchell Marner hopes the spotlight NHL players have can help those with the disease.

"That's what the goal is every day: to help change someone's life. We as players have the stage to do that," he said.

Hayden had the chance to meet players like Auston Matthews and Morgan Rielly, and coach Mike Babcock, who was touched by his 21-year-old forward's friendship with Hayden.

"He's a good kid, obviously," Babcock said. "He's not shy. When you are fortunate enough to get the gift of playing in the NHL and given the notoriety you have, you know you can make a difference and it's important you do.

"The other thing is, as important as this is to that young girl, it's that good for Mitch too. It's good for your heart, it's good for your soul."

Marner's best memory of that evening?

"The hug she gave me after the game. It was awesome," he said.

He hopes there are plenty of hugs in their future but knows there are no guarantees given Hayden's condition.

It has been a difficult time for the Foulons. Hayden's father, Jon, often has remained behind in London to work when his daughter has had treatments out of town. A fund called #GoTeamHayden has been set up on Facebook to help the family meet the costs of Hayden's treatments.

The family's other daughter, Harlow, 2, was 11 months old when she became Hayden's stem cell donor in March 2017. When Lindsay and Hayden were in Philadelphia for Hayden's treatments earlier this year, Harlow stayed at home with her dad.

"It's been tough, especially being separated from Harlow at times," Lindsay said. "But the most important thing is Hayden. Right now she has been feeling good. We've been concentrating on giving her the best Christmas we can. We'll deal with whatever comes up after that.

"We're just thankful for Mitch. He's been such a special influence in our lives."

Hayden said, "Mitch is my friend. I love him."

And vice versa.