Sergio Canlas Navarro, Jr., born on October 6, 1898 in San Fernando, Pampanga, wrote under the pen names ESY, Esiong, E. Sy Ong, Serna, Ibarra, Rex Moun, Conde del Sol, and Conde del Valle Inclan. A Capampangan poet and playwright, he studied at the San Francisco Xavier College, then an annex of Ateneo de Manila, Instituto de Manila, and Escuela de Derecho where he finished only two years of his law course. He became editor of the Pampango weekly Ing Kawal.
His “Napun, Ngeni, at Bukas” (Yesterday, Today, and Tomorrow) won first prize in the 1920 poetry contest sponsored by Ing Mananulin, the first Pampango magazine. His poetry collection was entitled Kasacmal a Sampaguita (A Handful of Sampaguitas), and his sarsuelas include Ninung Makikasalanan? (Who Is to Blame?), Indu Ku (My Mother), Ing Mapanako (The Thief), and Lua Ning Casalanan (The Tears of Sin). He also adapted foreign plays into Viuda Alegre(Merry Widow), Eku Kasalanan (It Is Not My Fault), and Siping Bale (Neighbor). Navarro passed away on March 12, 1972.