Things did not go entirely as expected for two former UFC champions making their debuts in ONE Championship on Sunday in Tokyo.

Longtime flyweight belt holder Demetrious Johnson defeated Yuya Wakamatsu via second-round guillotine choke in a fight that was surprisingly competitive, and Eddie Alvarez, a former lightweight titlist in both UFC and Bellator, was knocked out in the first round.

Alvarez (29-7, 1 NC) was shocked by Timofey Nastyukhin (13-4), a heavy-handed Russian who went at "The Underground King" from the start. Alvarez never got in a rhythm and was beaten to the punch several times, offering little in return. After being stunned by a right-left combination late in the round, he backed up against the cage and covered up. Nastyukhin unleashed a flurry of punches to finish the job at 4 minutes, 5 seconds.

"It's my style," said Nastyukhin, who advances in the Asian promotion's eight-man Lightweight Grand Prix. "I love to finish fights in the first round by knockout, so I did it."

The result was a cautionary tale for Johnson, who was up next to kick off the Flyweight Grand Prix. "Mighty Mouse" (28-3-1), who ruled UFC's 125-pound division for six years before being dethroned by Henry Cejudo in August, proceeded patiently against the power-punching Wakamatsu (10-4), 24, of Tokyo, who has nine knockouts among his 10 victories (five in the first round). Wakamatsu got the hometown crowd chanting, "Yuya! Yuya!" after he landed a crisp right hand late in Round 1, sending Johnson back to his corner with damage under his right eye.

"He's good about crossing distance, and the type of game he plays, he wants you to cross distance so he hits you with his right hand and left hook," Johnson said in a postfight interview inside the cage after addressing the crowd with a few of the Japanese words he has learned.

"So for me, I just had a hard time crossing distance carefully. I got caught right here," he said as he pointed to his bruised cheek, "but sometimes you battle through adversity in the cage or in life. You just keep on pushing through it."

Johnson brought the adversity to his opponent in the second round. The 32-year-old out of Kirkland, Washington, went to his grappling game. Half a minute in, Johnson countered an aggressive advance by Wakamatsu by taking him to the canvas. From there, Johnson swarmed with his trademark lightning speed, going from grappling transition to grappling transition. While dropping elbows and knees to the head -- the latter of which would have been illegal in a UFC fight -- Johnson continually looked for a submission. And just as Wakamatsu was scrambling to escape to his feet, Johnson locked in a guillotine choke.

"I've got a real nasty guillotine," Johnson said. "He went in for the [takedown] shot, so I put my hips in and he was hanging on to my legs, and that gave me even more of a torque to get the finish. I don't know if he went out or not ... but when he woke up, he was like, 'What happened? What happened?'"

What happened was Wakamatsu tapped out and the referee jumped in at 2:40 of Round 2.

A referee had jumped into the fight that preceded this one too -- to save Alvarez, 35, who has just one win in his past five fights, a skid that began when Conor McGregor took away UFC's 155-pound belt in 2016. Still, it was shocking to see Alvarez go down like this as he fought in Tokyo just hours after UFC had held an event in his native Philadelphia.

Belying the glittery possibilities of bringing in a pair of UFC greats, this was clearly an Asia-centric event. Rather than put Johnson and Alvarez at the top of the marquee for an event the promotion billed as "A New Era," ONE Championship stashed them below four title bouts on the card. Strawweight Jingnan Xiong (fifth-round TKO of atomweight champ Angela Lee) and middleweight Aung La Nsang (second-round TKO of Ken Hasegawa) successfully defended their belts, while welterweight Eduard Folayang lost his title to Japanese legend Shinya Aoki via first-round submission and bantamweight Kevin Belingon was disqualified in Round 3 against Bibiano Fernandes for delivering strikes to the back of the head, handing the strap back to the man he had taken it from in November.

But this was a night owned by Johnson, at least for North American fans who tuned in early to watch the former pound-for-pound No. 1. He joined ONE Championship in October in what was essentially a trade with UFC; in exchange for allowing him to sign with the Singapore-based promotion, UFC was granted permission to bring on former ONE welterweight champ Ben Askren, who had retired undefeated.

Now Johnson, whose 11 title defenses are a UFC record, is in pursuit of glory in the ONE tournament.

"I can't wait for the next round," he said.