It was the perfect response for Ledecky, who was dethroned and left disappointed by the record-breaking Ariarne Titmus in Sunday's 400m freestyle event.
Earlier, Richards finished strongly to bag the gold ahead of compatriot Tom Dean in his freestyle event with a solid time of one minute, 44.30 seconds.
"I knew going into the race it was one of the most stacked 200 freestyle fields for a long time.
Olympic champion Dean finished 0.02 seconds behind to take silver and Hwang Sun-woo of South Korea took the bronze, while 2022 world champion David Popovici of Romania missed out on a podium spot.
She charged to victory in the event in 57.53 seconds to edge out 2022 world champion Regan Smith of the United States by 0.25 seconds and Katharine Berkoff by 0.72 seconds.
Persons:
Katie Ledecky, Marko Djurica, Matthew Richards, Ledecky, Simona Quadarella, Li Bingjie, I'm, Richards, Tom Dean, Dean, Hwang Sun, David Popovici, Kaylee McKeown, Australia's, Regan Smith, Katharine Berkoff, McKeown, Smith, Italy's Thomas Ceccon, Ryan Murphy, Murphy, Hunter Armstrong, Lilly King, Lithuania's Meilutyte, Shrivathsa Sridhar, Toby Davis
Organizations:
Marine Messe Fukuoka, Britain, London Games, Thomson
Locations:
Fukuoka, Japan, Marko Djurica FUKUOKA, United States, British, South Korea, Romania, Barcelona, Bengaluru