A decade after quitting as a burnt-out 18-year-old, Tu advanced to the second round of the Adelaide International on Tuesday.
Australia's Aleksandar Vukic and Adam Walton dipped out with first-round defeats at Memorial Drive, as did James Duckworth, who Tu defeated 6-1 7-5.
Tu used to fight Thanasi Kokkinakis for Australia's top junior status before walking away from the sport for eight years.
"I wasn't playing," he said.
"I did uni. I was a waiter. I was a delivery driver for a long time."
Tu returned after a stint coaching juniors rekindled his love for tennis and, after three years on the circuit, he's now preparing for a late bloom.
"I know I'm 28 but I only started playing it three years ago - I had no ranking three years ago," he said.
"I still feel so fresh.
"I did one year and on the Futures (tour), and then two years on Challenger (tour) and I feel like every year I'm learning more about myself, learning more about what this is about, and what it really takes.
"I feel very upbeat ... I feel really young on the tour, to be honest."
Ranked 179 in the world, Tu has set his sights on cracking the top 100 Â after experiencing the big time last year with a US Open clash against Carlos Alcaraz at the famed Arthur Ashe Stadium.
Tu took a set off the Spanish gun and collected his largest pay day, a $US100,000 ($A160,000) cheque, for his first-round loss after successfully qualifying.
"It was 27,000 people and not a whole lot can prepare you for that," he said.
"The most people I played in front of before that was maybe 3,000.
"I did a lot of visual visualisation the night before the morning of and but I still walk out and I'm like: 'Whoa ... it's still so big'."
Tu will meet French qualifier Benjamin Bonzi in the second round in Adelaide, and could yet run into Kokkinakis in the semi-finals.
Eighth seed Tomas Etcheverry will face Kokkinakis on Wednesday for a place in the last eight after the Argentine eliminated Australian wildcard Tristan Schoolkate 7-6 (10-8) 6-3 in Tuesday's feature night match.
But a trio of Australians fell on day three.
Vukic was beset by a batch of late errors in his three-set loss to Marcos Giron.
The American prevailed 6-2 3-6 6-3 as Vukic made 17 unforced errors in the last set.
Queenslander Walton suffered a straight-sets loss to Arthur Cazaux, the Frenchman winning 7-5 6-1.
Another Frenchman, world No.261 Manuel Guinard, also advanced with an upset 7-6 (7-4) 2-6 6-1 victory against Russia's world No.62 Roman Safiullin.
And American seventh seed Brandon Nakishima beat German qualifier Yannick Hanfmann 6-1 2-6 6-3.
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