Japan's Yasuhiro Koseki shook off a slow morning heat to win the men's 100-meter breaststroke gold from Lane 1 at the Asian Games on Wednesday.

The 26-year-old's gold, won in 58.86 seconds, completed a 100-200 breaststroke double, and with the 50 to come on Friday, he has a chance of taking a hat-trick of medals in the stroke.

Japan saw more gold later when Daiya Seto clocked 4:08.79 to beat reigning Olympic champion Kosuke Hagino by 1.51 in the men's 400 individual medley. China's Wang Shun was third.

Seto's gold was his second at this edition of the Asian Games and fourth in total.

"It was so tight my head was pounding, and that was my plan," said Seto. "I have had a lot of comfortable races recently, and all the easy races I have had would make it difficult for me to win gold in Tokyo."

"This was my season's best time, it was a race that makes me think I'll be able to handle the Tokyo Olympics."

(From left, Kosuke Hagino, Daiya Seto and Wang Shun after the men's 400m individual medley final)

Natsumi Sakai won her second gold of the games when she swam a 59.27-second women's 100 backstroke final. The 17-year-old reigning world junior champion over 50 beat her compatriot Anna Konishi by 0.40 and China's Chen Jie by just over a second.

Japan continued a superb night in the pool when its men's 4x100 freestyle squad -- made up of Shinri Shioura, Katsuhiro Matsumoto, Katsumi Nakamura and Juran Mizohata -- beat China by half a body-length. The Japanese set a games record of 3:12.68 with Singapore finishing in third.

Earlier, Olympic men's 100 butterfly champion, Joseph Isaac Schooling of Singapore, took the gold in a games record 51.04-second time.

China's Li Zhuhao finished second and Japanese veteran Yuki Kobori won bronze, his fifth Asian Games medal and second here after his gold in the 4x200 freestyle.

(Yasuhiro Koseki in the men's 100m breststroke final)

China's Li Bingjie won a tight women's 200 freestyle, establishing her winning margin with a strong final 50 meters as she held off compatriot Yang Junxuan.

Yang stretched to the wall just 0.01 ahead of Japan's Chihiro Igarashi, who won her first individual medal of the games in Indonesia.

In the women's 200 butterfly Zhang Yufei was too fast for the Japanese pair of Sachi Mochida and Suzuka Hasegawa. The Chinese swimmer touched in 2:06.61 with the silver and bronze medalists both more than 2 seconds adrift.

In the mixed 4x100 medley relay, China took bragging rights, holding off Japan, in a games-record 3:40.45. Japan took silver, 0.76 back, while South Korea placed third, far off the pace in 3:49.27.

(Rikako Ikee in the mixed 4x100 medley relay)