Dad's Reaction to Daughter's Fitting Room 'Fashion Show' Goes Viral, But Their Backstory Goes Deeper (Exclusive)

"He's just the best soul I could have in my life," Haas tells PEOPLE of her stepfather, who entered her life at age 4 and has been called "dad" ever since

This father-daughter duo turned a fitting room into a fashion show.

Katie Haas went viral on TikTok for a video showcasing her stepdad's unwavering support of the clothes she tried on when shopping one day, a heartwarming interaction that prompted her to give him the "personal hype man" nickname.

The bond shared between the pair is, in part, the reason why Haas has more than 500,000 followers on the app. Her videos are raw, real and delve into her family dynamics in an attempt to spread awareness around mental health and parental relationships.

In an exclusive interview with PEOPLE, Haas opened up about her bond with her stepdad, explaining why she doesn't call him by that title, and shared the inspiring reason she transparently posts such personal content on her TikTok.

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Haas, a 29-year-old elementary school teacher from New York, was introduced to her stepdad at age 4. It wasn't until she was 22 years old that she met her birth father for the first time, after "not knowing a thing about him" growing up, she shares.

While she says she's still in the process of "building a bond" with her birth father, Haas says she's been calling her stepdad "dad" ever since she was young. "He is more my father than anyone else on the planet," she says, adding, "He calls me his daughter, too."

Haas uses her following to advocate for those with mental health conditions and has opened up on TikTok about her dad's diagnosis. She explains that he has OCD and schizoaffective disorder, which in his case, she describes as "a combination of schizophrenia and bipolar disorder."

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Spending time together growing up is why their relationship was so tight from the start.

"I would just always listen to him, talk to him and give him my advice as a child," she shares. "As the youngest, I just went around and took care of everybody in every way possible, emotionally and physically."

In several videos, Haas has detailed her parents' split later in life, retelling the story of how she reconnected with her dad (who prefers to go by "Katie's dad" online) and sharing footage from their get-togethers since.

Haas also assures her dad is "okay with [her] sharing" details about his life, especially since she intends to make others "feel more comfortable talking about their mental health" and see the rewards of a "loving relationship."

Many of Haas' followers are drawn to her videos because of her dad's "amazing, pure spirit." She says her dad "has no filter" and will "say 'Hi' to you" regardless if he knows someone or not.

"He will greet you like he already knows you and he really just spreads joy to everyone that he's around," Haas continues of her dad. "He's full of compliments and kindness. He's just the best soul I could have in my life."

While Haas says her dad is "very engaging" with the people he meets, she says sometimes he experiences not-so-nice interactions. "If they're not a good, nice person ... then they ignore him and my dad just brushes it off," she says. "He doesn't really care at all."

For those who do exhibit kindness toward him, Haas says "it really touches my heart." She explains, "I like to see the light in him. I like to see it be spread throughout whoever he interacts with. It really touches my soul."

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"I don't try to suppress anything that he wants to do and I never get embarrassed of him either," Haas continues. "Because if he's not embarrassed that he has a stain on his shirt, why should I be ... as long as he's happy and comfortable."

In a similar fashion, that's exactly how Katie's dad strives to make her feel, too, which is what drew viewers to her TikTok video in the store dressing room. "We call it our little fashion show," Haas says.

"He likes to see everything that I try on. I just try it on, I come out and always film it because I know his reaction is so genuine and sweet," she explains, recalling her dad's super-supportive response to a solid-colored shirt she thought "was nothing special."

"He literally is my biggest hype man," says Haas — and it's clear that she's his, too.

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