Floyd Mayweather and Manny Pacquiao reignited their old rivalry while on a stage together in Japan

• Floyd Mayweather and Manny Pacquiao were reunited on a Rizin stage Saturday.
• The two boxers fought in one of the best-selling bouts of all time in 2015. Mayweather won.
• The pair reignited their old rivalry with Mayweather warning Pacquiao may get his ass whooped again.

Floyd Mayweather and Manny Pacquiao were reunited on a stage Saturday in Japan and did not take long to reignite their old rivalry.

Retired American boxer Mayweather defeated Filipino fighter, Pacquiao, by 12-round decision in a 2015 super fight that was years in the making.

Though Mayweather retired in 2017 after besting UFC star Conor McGregor in a crossover match, he remains in the spotlight because of how he's reinvigorated the exhibition boxing scene.

Having recently moved around with Tenshin Nasukawa, Logan Paul, and Don Moore he now, on Sunday, competes in an unofficial bout against MMA star Mikuru Asakura. It will air Saturday on PPV.com in the US.

Ahead of the Rizin 38 show in Saitama, Japan, Mayweather came face-to-face with Pacquiao, who said he was there to support his boxer Asakura.

Mayweather and Pacquiao verbally sparred

"There's no blueprint on how to beat Floyd Mayweather and he can tell you that himself," 45-year-old Mayweather said of Pacquiao.

"When we talk about Hall of Famers, he's a Hall of Famer. But nobody has the remedy on how to beat Floyd Mayweather."

Wagging his finger at Pacquiao, 43, Mayweather added: "Don't let them trick you into getting your ass whooped again."

Responding, Pacquiao said: "He's older than me. I'm still young, what I have done and accomplished in boxing, it's one of a kind. To get here, an eight-division world champion is not easy."

Comparing their resumes in boxing, Mayweather riffed on his undefeated status.

"When it comes to what's going on in that squared circle, I'm the best," he said.

"No matter how you grade it, how you slice it, how you cut it — if you go 100 years back, 300 years back, all the way to know. There's only one best, and that's Floyd Mayweather."

Mayweather appears to be on the hunt for future opponents

Whether Mayweather and Pacquiao are attempting to generate interest in a rematch is, for now, unclear.

But the Las Vegas-based fighter is targeting opponents as he said earlier this week that he'd fight Conor McGregor in an official bout. It would be his 51st pro contest, should it happen.

"Hopefully me and Conor McGregor can lock up in 2023 in a real fight," he told TMZ Sports.

McGregor did not seem keen on the proposal as he posted on Instagram — in a since-deleted message — to say he's "not interested."

This is a contrast to how he seemingly felt in July when the two marquee fighters were arguing over the ruleset for a prospective mega match.