Complex sentence: Toshihiko Seko (瀬古利彦, Seko Toshihiko, born July 14,1956 in Kuwana, Mie) is a Japanese long-distance runner, a world-class marathon competitor in the 1980s.
Split into simpler sentences: Toshihiko Seko (瀬古利彦, Seko Toshihiko; born July 14,1956 in Kuwana, Mie) is a Japanese former long-distance runner. He was a world-class marathon competitor in the 1980s.