The city government announced the discovery of Akechi Mitsuhide's Sakamoto Castle on Feb. 7. He is believed to have led the coup against Nobunaga, who was on the verge of unifying Japan.

The festival was launched in 1973 to honor the warlord Akechi Mitsuhide, and includes a majestic procession of historical re-enactors portraying Mitsuhide and his entourage. Last year, the ...