Japan's Natsumi Tsunoda shrugged off an injured back to win a gold medal Wednesday, scoring a convincing victory over South Korean Park Da Sol in the women's 52-kilogram class on the first day of the judo competition at the Asian Games.

While Tsunoda, the 2017 world silver medalist, had a clear ippon victory against the unheralded Park, Japan's three other judoka competing in finals the same day had to settle for silver at the Jakarta Convention Center's Plenary Hall.

Ami Kondo, the 2014 world champion, fell in the golden score to Rio Olympic silver medalist Jeong Bo Kyeong at 48 kg, while men's judoka Toru Shishime and Joshiro Maruyama lost their respective finals, to Uzbekistan's Diyorbek Urozboev and South Korea's An Baul at 60 kg and 66 kg.

(An Baul, left, defeats Joshiro Maruyama)

"I had a lot of pressure to win so I am relieved I could do it," said Tsunoda. "I am known for my tomoe-nage and juji (gatame) but I'm glad I was able to mix in other techniques and keep my opponents off-balance in my bouts today," said the 26-year-old, referring to the backward rolling circle throw and armlock technique she deployed against Park to secure her victory.

Tsunoda, who strained her back a week ago and could not practice since in the run-up to competition, deployed the tomoe-nage technique for a waza-ari before finishing off the match with a vice-grip armlock at 2 minutes, 18 seconds.

"I didn't have any serious injuries all year but then I strained my back. I felt like a grandmother," she said with a laugh. "But actually it happens when I do a lot of practice before a tournament."

Tsunoda said with the Asian Games gold, she could show that she is also as competent for a spot on the Japan team, possibly for the 2020 Tokyo Olympics, in the hotly contested 52-kg category, featuring 18-year-old ace Uta Abe and last year's world champion Ai Shishime.

"If I had lost in the Asian Games, I was for sure I'd lose a lot of ground to Abe and Shishime but I could make my presence felt in a big way. I think I managed to cling on" in the race for the national team, she said.

(Natsumi Tsunoda, 2nd from left, poses with her gold medal)

The 23-year-old Kondo, meanwhile, was in tears as she again failed in her bid to win the title at an international competition, after a bronze finish in the Rio Olympics and at the world championships last year.

Compatriot Funa Tokina claimed the gold at the 2017 worlds and has booked a ticket to the world championships next month.

"I fought with the determination to win a title this year but again I couldn't. I am always one step away from winning gold medal. I have to think about how to actually win it," she said.

Despite the loss against Rio bronze medalist Urozboev, it was an improvement for Toru Shishime who could only manage a bronze medal in the previous Asian Games in Incheon, South Korea in 2014.

Even so, he was not satisfied. "I couldn't perform my judo at all...silver is meaningless. Only the gold medal counts."

(Urozboev, right, and Shishime)

In the final and fourth gold medal match, Maruyama was tossed to the mat when Rio silver medalist An executed a seoinage shoulder throw 50 seconds into the match for an ippon.

"I was moving smoothly until the final bout. But I still have a long way to go...I was not thoroughly prepared," said Maruyama, his voice shaking.