Complex sentence: Unusually in the sumo world, his family name, Shimotori, is the name he uses as his fighting name, for a short interim changed his fighting name to the the similar sounding Shimoōtori, but has since returned again to using his family name.
Split into simpler sentences: Unusually in the sumo world, his family name, Shimotori, is the name he uses as his fighting name. For a short interim, he changed his fighting name to the the similar sounding Shimoōtori, but has since returned again to using his family name.