Shishite Ikiru SSS-kyuu Hunter

A mysterious tower crawling with monsters has suddenly appeared, drawing Hunters willing to risk their lives for glory and riches. Gong-Ja Kim, a weak F-rank Hunter, spends his days envying the Flame Emperor who reigns as the top Hunter. But his chance at greatness finally arrives when he joins forces with the Sword Emperor and gains a rare S-rank skill, with one catch: he must die to activate it.

(Source: Crunchyroll, edited)