Sunday's time, therefore, sounds a strong warning to Liu's rivals ahead of the Tokyo Olympics, and has inevitably led to expectations that she could challenge Sjostrom's world record (23.67), which was set at the 2017 worlds in Budapest.

Typically, though, the soft-spoken Guangzhou native chose to keep her feet on the ground.

"The disappointing 2019 worlds campaign was a big blow and made me doubt myself and whether I could still push for improvements," said Liu.

"Now with my confidence back, I think I can still improve a lot in my core strength, my starting and my underwater kicking.

"I won't think too much on how fast I can swim (in Tokyo). I will only focus on how much I can push myself in training."

Regarded as an exceptional backstroke sprinter early in her career, Liu shot to prominence at the 2018 Asian Games in Indonesia, where she became the first woman to break the 27-second barrier in the 50m back (26.98).

The standout performance saw the photogenic star dubbed a "swimming goddess" by fans, however, she shies away from talk about her supermodel looks.

In a recent interview with Tencent, Liu said she'd rather earn fame purely for her swimming ability than be considered a "vase in the pool".

Four golds at the Champions series' Shenzhen and Beijing stops over the last week sends a strong signal to Liu's international rivals, according to Liu's coach, He Xinzhong.

"She's now more confident than ever and that came from a solid physical training program which has produced encouraging results," said He, who has coached Liu since 2010.

With 50m back not included in the Olympic program, He said that Liu will only focus on freestyle in the build-up to Tokyo, with her training tailored to enhancing her leg strength.

This is the second edition of the FINA Champions Swim Series, which requires a higher entry benchmark than the World Cup circuit. With no heats, each event is contested by just four swimmers.