Kellie Harrington claimed a comprehensive unanimous-decision victory over Italy's Rebecca Nicoli in their lightweight round of 16 bout.
The Irish flag-bearer lived up to her billing as top seed in the division, putting on a masterclass of controlled and composed boxing to book her place in the quarter-finals, where she will fight for, at least, a bronze medal against Imane Khelif of Algeria (4.35am, Tuesday).
Harrington started strongly and put her stamp on the fight from the first bell, taking up position in the middle of the ring and showing more aggression as she looked to sound out her opponent.
Nicoli did grow into the round as the two traded punches with neither fighter really dominating before Harrington stepped things up in the final minute of the round, landing with some really solid combinations before pulling back out of danger.
All five judges gave the round to Harrington who then continued the second round in the same vein she ended the first - picking her punches, landing quick flurries and dancing back out of reach of her opponent.
The fight was being fought at Harrington's pace and while Nicoli was landing here and there, she was getting caught by the Irish woman who was relishing fighting on the counter and making the Italian pay for every punch she threw.
Again all five judges gave the Dublin fighter the nod and going into the final round, Nicoli knew she had to produce something very special to stop Harrington.
Having the Italian chase the fight just played into Harrington's hands and the Irish woman invited her on, stepped back out of danger and then tagged Nicoli seemingly at will.
Switching back from southpaw to orthodox to keep Nicoli off balance, Harrington safely saw out the fight and although one judge called the third round for the Italian, Harrington marched into the quarter-finals.
There will be bigger challenges ahead for Irish woman, but given her performance today, there’s no reason to believe she won’t rise to them.
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After a month in Japan, Harrington - the last Irish boxer to enter competition - was just relieved to get the first fight over and done with.
"Get the ball rolling. The first one is always the hardest anyway I feel," said Harrington.
"I'm glad to get started and underway, I was a bit anxious coming in. Last person to box really. The support from the rest of the team has been amazing, and Brendan [Irvine, team captain] has been keeping the rest of the team going - he's a true leader in every aspect," she told RTÉ Sport.
Despite the long wait, Harrington said she had not been obsessing about this fight, but rather maintaining her fitness and preparing properly.
"I started focusing today on the fight. I'm fit, I'm sharp. I have the coaches there, and my own club coach Noel Burke at home, keeping me focussed.
"Today is the day when you have to switch on, otherwise you burn out too soon," said the 31-year-old, who will take a similar approach to Tuesday's bronze medal bout.
"I haven't even thought of [winning a medal], just roll on to Tuesday and I'm just fighting for myself, fighting for my own honour and what will be will be.
"If I get a medal that will be great, but as long as I give it everything, as long as I step out of the ring knowing that I have given everything I will be happy."
Top-seeded Harrington will be fancied to overcome Khelif, but she is not underestimating any opponents in Tokyo.
"Personally I don't believe there are any top seeds because everyone at the Olympic games has had a hard way of getting here, so we're all top drawer out here, we're all elite athletes.
"It's who shows up on the day really and anything can happen."