"It has taken a lot of dedication to get here today as champion. This season I came back well prepared so I'm really happy with the result," Lee said.
"I used the right techniques against my opponent because I've played against him before and know what strategies to use."
Those expecting a comfortable win for China's He Bing Jiao in the women's final got a surprise, as 17-year-old Japanese qualifier Saena Kawakami pulled off the biggest win of her career.
Kawakami won the first game in 15 minutes and took out the match in 43 minutes, 21-16 21-18.
"I'm really happy but I haven't really thought about how I won yet, I'm feeling a bit overwhelmed by it all," Kawakami said. "It was a hard game but I was focused today. I was persistent and didn't make a lot of errors. That helped me to win."
Japan has form in this event in recent times. Last year, Kawakami's compatriot Nozomi Okuhara won the title; two years ago Akane Yamaguchi finished runner up, then went on to win the world junior title.
The women's doubles final was a thriller; fourth-seeded Chinese pair Xia Huan and Zhong Qianxin fought back from the brink of defeat to win 17-21 24-22 21-19 against Japan's third seeds Yuki Fukishima and Sayata Hirota.
There were some spectacular rallies, and the Chinese combination saved a handful of match points in the second game. China's 18-year-olds Huang Kaixiang and Zheng Si Wei rallied from losing the first game to beat Indonesia's Fajar Alfian and Muhammad Rian Ardianto 16-21 21-17 21-9 in the men's doubles final.
In an all-China mixed doubles final, Zheng Si Wei and Chen Qingchen were too strong for Yu Xiaoyu and Xia Huan, winning 21-14 21-8.
