The 27-member Fujisawa choir, which is beginning a week-long concert tour of Wales, has spent several months listening to audio tapes to learn the Welsh words phonetically.
The result will be renditions of "Tydi a Roddaist" (Thou Who Gavest) and "Laudamos" at venues in Pembroke, Swansea, Ebbw Vale and Cardiff.
The choir was keen to attempt the Welsh hymns because Japan, like Wales, has a particularly strong choral tradition.
Alun John, the Cardiff choral conductor and teacher who organised the tour, said: "We are all looking forward with great anticipation to hearing the results."
His wife, Rhiannon, recorded special versions of the hymns on audio tapes which were sent from Cardiff to Japan to coach the choir.
Mr John explained: "Japan, like Wales, has a strong choral tradition and the Fujisawa choir has a very good reputation. They asked to sing something in Welsh and will be taking part in joint concerts with local choirs".
The Fujisawa choir, which is based 35 miles from Tokyo, includes company executives, factory workers and schoolteachers and its members range in age from 24 to 70.
The choir also plan to sing "We'll Keep a Welcome in the Hillsides" in English and "All Through the Night" in Japanese.
The choir is following a firm tradition of Welsh-Japanese musical links, strengthened by the fact that Wales has the largest concentration of Japanese industry outside Japan.
Japanese conductor Tadaaki Otaka was musical director of the National Orchestra of Wales for nine years and took the ensemble to Tokyo for his final concert in charge in 1995.
Aled Jones, who captured the hearts of the nation with his haunting and angelic soprano singing, had 16 number one hits in Japan. He recalled: "There were thousands of screaming young girls at the airport. I thought, God, this is fantastic. But my chat-up lines were limited. I was there to narrate Hansel And Gretel and the only Japanese I knew was `do you want to look round my gingerbread house?'"
And one of Wales's premier "Welshpop" - as opposed to Britpop - bands, Gorky's Zygotic Mynci, have proved to be a hit with teenage girls in Japan where fans have the band autograph English-Welsh dictionaries.