Webrengoku was killed off in the series since it would serve as an important plot point, and his death would play a crucial role in tanjiro's character progression.
Webso when he was asked about rengoku's death and how tanjiro reacted, hanae said their final talk left him in tears.
According to hanae, the chat got to him.
Webtragically, the upper moon 3 demon ultimately killed him in the second season, prompting the question—why was rengoku’s character eliminated?