Solo Leveling, Vol. 4 (Comic)

"When Jinwoo sets about mentoring one of Jinho's recruits--who also happens to be his sister's good friend ... a White Tiger Guild training operation seems like the perfect opportunity to show her what being a hunter really entails. But the moment he and Songyi enter the gate, Jinwoo realizes something is wrong. With a flash of red, the exit vanishes, stranding them and the White Tiger trainees in a frozen forest for what could be weeks--or until someone can defeat the dungeon's formidable boss"--