Kristie Ahn walked off Court 5 with an inimitable smile, with her first Grand Slam win, with a feeling she’d long ago convinced herself would never come.

Her father, Don, struggled with the reality, too.

“My dad was like, ‘So, this is a bit of a problem. … How are you gonna get into corporate America if you keep winning?’ ” the Stanford graduate said. “He’s very keen on me hanging up the racket and getting a 9-to-5 job, but I’m gonna try and milk this as long as I can.”

Playing in the U.S. Open main draw for the first time since debuting as a 16-year-old qualifier 11 years ago, Ahn defeated former U.S. Open champion Svetlana Kuznetsova 7-5, 6-2 on Tuesday.

Then, the New Jersey journeywoman — who’d planned to quit the sport after the 2017 season — handed her laundry to her parents.

“I made a deal with my parents — they kind of helped me from 2014 to 2017 financially, and my dad, literally, I swear, had a calendar countdown, saying, ‘We’re almost there. It’s almost the end of 2017. Get ready to look for jobs. Do you have a résumé ready?’ ” Ahn said. “Now, my dad’s worried.”

Growing up in nearby Upper Saddle River, Ahn became one of the top-ranked junior tennis players in the country, and the youngest in the 2008 U.S. Open field, when she lost to sixth-seeded Dinara Safina 6-3, 6-4.

“First-round prize money was $18,500 and as a 16-year-old, you’re like, ‘Oh my god, so much money, let me take it.’ … My dad deadpanned a face, ‘You could win the U.S. Open this year and you still would go to college,” Ahn said. “It’s funny because when I was like 16, I was like, ‘Oh yeah, I’ll be here next year again.’ And when I was 17, I was so burnt out. You’re just so green and have no idea what’s going on. … I felt like it was too much, and I told my mom I’m gonna work at Panera.”

Ahn, whose parents immigrated from Korea, went to Stanford where she became an All-American, and received a degree in science, technology and society.

She then joined the tour full-time, but a top-100 ranking would never come. The travel wasn’t worth the early tournament exits. The money wasn’t worth the travel.

A dream job was a constant source of frustration, with Ahn continually haunted by the prospect of peaking at 16.

“All these questions start looming above your head, so now it’s all like tucked away — and good riddance,” Ahn said. “I feel like I can finally put the 2008 U.S. Open to rest. May it rest in peace. … It’s no longer that looming skeleton in my closet anymore. I can play free. And I feel like I have.

“In the past couple years I’ve kind of struggled with the feeling of belonging. I felt something was lacking. I felt like I was fortunate to be there, like this won’t last type of thing. … Now, when I go out there, I don’t feel nervous. I just go out there and enjoy it.”

The last match of Tuesday’s schedule didn’t begin until after 11 p.m. and ended after 1 a.m. Wednesday, with Nick Kyrgios delighting the crowd with some trick shots while beating Steve Johnson 6-3, 7-6 (1), 6-4.

Also Tuesday night, three-time champion Rafael Nadal, the No. 2 seed, rolled past John Millman, 6-3, 6-2, 6-2.