Kitajima won the 100m breaststroke on Monday in world-record time.
"I was going OK until the last 50 metres, and then I ran low on energy, but it was a good swim and I am pleased with the time," he said.
On another day of action in the Beijing Water Cube, Thursday morning also saw the final of the men's 100m freestyle with Frenchman Alain Bernard beating back a challenge from Australia's Eamon Sullivan to take gold.
Bernard touched in with a time of 47.21 seconds on Thursday, with Sullivan, the world-record holder, taking the silver in 47.32.
|Thursday saw a relatively quiet day for Michael Phelps [GALLO/GETTY]
American Jason Lezak and Cesar Cielo of Brazil tied for the bronze in 47.67.
In the women's events China's Liu Zige gave the host nation its first swimming gold medal of the Beijing Olympics, winning the women's 200m butterfly in a world record time of 2:04.18.
Her time shaved more than a second off the previous mark set by Jess Schipper of Australia at the 2006 Pan Pacific championships in Canada.
A day after scoring his fourth and fifth golds at the Beijing games, Thursday was a relatively quiet day for US swimming ace Michael Phelps, now the Olympian with the most golds ever.
Although not competing for any medals, he confirmed his place in Friday's 200m individual medley final, setting himself up for what would be his 12th Olympic gold.
The American won his semi-final heat on Thursday morning with a time of 1:57.70, marginally slower than his teammate and main rival, Ryan Lochte, who won his heat in 1:57.69, making him the top qualifier.
Phelps is aiming to take three more medals in Beijing, breaking the 1972 record of US swimmer Mark Spitz who won seven golds at a single games.