The demon that appeared before Tanjiro and Rengoku after they defeated Enmu was the Upper Three, Akaza. While injured and on the ground, Tanjiro is almost attacked by Akaza and narrowly escapes death when Rengoku quickly strikes back. During the intense battle between Rengoku and Akaza, Akaza suggests to Rengoku that he should also become a demon. Rengoku vehemently refuses Akaza's offer, but his injured body is exhausted and being pushed past its physical limits...
Anyone who risks their lives
fighting demons to protect humans...
Aquellos que se enfrentan a demonios
para proteger a otros,
Cualquiera que se juegue la vida
protegiendo a los demás de los demonios,
Lutar com Onis arriscando a própria 
vida para proteger humanos…