The youngster defeated Brazil's Hugo Calderano in a marathon semi-final at the OMEGA Sport Center in Olomouc.

He always recovered from the jaws of defeat before winning 6-11, 12-10, 4-11, 11-4, 11-9, 9-11,16-14.

"It is unbelievable that I won after my opponent had five match points," said Harimoto.

"I have not been thinking about the final. 

"I was concentrating only on this match."

Harimoto will be the youngest-ever ITTF World Tour winner if he beats German top seed Timo Boll in tomorrow's final.

He beat Frenchman Emmanuel Lebesson in routine fashion, 11-3, 11-9, 12-10, 12-10.

Both the quarter-finals and semi-finals were played on the same day today.

Boll had earlier beaten Sweden's Par Gerell in straight games in the last eight, 11-6, 11-6, 11-8, 11-7.

Lebesson ousted Jin Ueda of Japan in six, 11-13, 12-10, 11-5, 11-7, 9-11,11-6.

There was also an epic quarter-final for Harimoto who came through in seven against Kristian Karlsson of Sweden.

The Japanese teenager eventually won 11-9, 7-11, 11-4, 9-11, 12-10, 9-11, 11-6.

Calderano also needed to come through a match which went the distance.

He eventually beat Yun-ju Lin of Chinese Taipei 3-11, 10-12, 11-7, 14-12, 8-11, 11-9, 13-11.

In the women's event, the final will be an all Japanese affair between Kasumi Ishikawa and Mima Ito.

It will be a repeat of the Bulgarian Open final last week which Ishikawa won.

Today, top seed Ishikawa knocked out another team-mate in Yui Hamamoto, 11-6, 12-10, 13-11, 11-9.

Ito beat German second seed Han Ying 11-5, 6-11, 12-10, 11-5, 11-5.

In the women's quarter-finals, Ishikawa defeated Chinese Taipei's Yi-Hua Huang 7-11, 11-4, 11-13, 11-4, 11-3, 11-2.

Hamamoto won an all-Japanese affair against Hina Hayata, coming from 2-0 down to prevail 7-11, 8-11, 11-9, 11-7, 11-8, 11-5.

Ito beat Hungarian Georgina Pota 7-11, 11-5, 11-9, 11-9, 8-11, 13-11.

Han was too strong for Honoka Hashimoto of Japan, 11-1, 11-7, 5-11, 16-14, 11-5.