Around 50 producers and sellers gathered on Tuesday, where a Shinto priest offered prayers and a representative presented a sacred tree branch.
Women in aprons and red sashes sang as they demonstrated the noodle-making process, using strands of white wool to symbolise the thin wheat noodles.
Somen has seen sales decline in recent years, but demand rose this year amid intense heat.
An industry cooperative official said efforts will continue to raise awareness of the high quality of locally produced somen.
