The 16-year-old was hoping to regain the title he won in 2017, but, despite taking a 2-0 lead, he fell to an 11-3, 11-7, 8-11, 11-7, 9-11, 9-11, 7-11 loss at the OMEGA Sports and Health Center.

Pletea's reward for his highly-impressive victory is a round-of-16 meeting with another Japanese player, Yuki Hirano, tomorrow.

Hirano progressed today by beating home player Pavel Sirucek 11-7, 12-10, 9-11, 11-9, 9-11, 11-4.

Also through is second seed Hugo Calderano after he defeated fellow Brazilian Gustavo Tsuboi 11-5, 12-10, 11-9, 4-11, 11-6.

Fifth seed Koki Niwa of Japan and eighth seed Liam Pitchford of England joined Harimoto in crashing out at the first hurdle.

Niwa was beaten 11-4, 9-11, 7-11, 4-11, 13-15 by Portugal's Marcos Freitas, while Pitchford was defeated 5-11, 11-6, 6-11, 13-11, 3-11, 8-11 by Russia's Alexander Shibaev.

Top seed and defending champion Kasumi Ishikawa of Japan survived a seven-game thriller against Chinese Taipei’s Cheng Hsien-Tzu, winning 11-7, 7-11, 8-11, 11-2, 6-11, 11-1, 11-2.

She will go onto face China’s Xi Liu, who had no problems in overcoming Puerto Rico’s Adriana Diaz 11-4, 11-7, 11-9, 11-9.

The highest-seeded player to be eliminated from the women's singles event was 12th-ranked Miyu Kato of Japan.

She lost 11-5, 11-13, 7-11, 5-11, 4-11 to China's Liu Weishan.

Action in Olomouc is due to continue tomorrow.