그렇게 혼자 참다가는 너 무너져

The line, explained

Concern often sounds like a warning. 'If you keep this up, you'll get hurt.' Korean builds that sentence with a single ending, -다가는, which takes whatever someone is doing and projects it forward to a bad end. Parents use it, friends use it, and film characters use it in the quiet scene where someone finally says what they have been worrying about. Today's line is that scene, on a rooftop at night.

그렇게 means 'like that', pointing at the behaviour in question. The ㅎ and ㄱ merge to give geu-reo-ke. 혼자 is 'alone, by yourself', a word fans know from countless sad songs. Together, 그렇게 혼자 frames the problem: not just holding it in, but doing it alone, without letting anyone help. In the context of the film, the speaker has watched their friend smile through everything and has finally had enough.

참다가는 is the heart of the line. 참다 means 'to hold back, to endure, to put up with': you 참다 tears, anger, pain or a sneeze. -다가 on its own means 'while doing, and then'. Add the topic marker 는 and it becomes a conditional warning: if you go on holding it in. The ending attaches to any verb with no changes.

너 무너져 is the consequence. 너 is 'you', and 무너져 is 무너지다, 'to collapse, to crumble', in the casual present. Buildings 무너지다, and so do people. Korean often uses the plain present for a near-certain future in warnings, which makes it sound blunt and immediate: you will break. You could also say 무너질 거야 (you will collapse) or 무너지겠다 (you look like you'll collapse), each a shade softer.

The pattern is a natural for nagging: 그렇게 먹다가는 살쪄 (keep eating like that and you'll put on weight), 그렇게 일하다가는 쓰러져 (keep working like that and you'll keel over). In fast speech it shortens to -다간, so 그러다간 다쳐 means 'keep that up and you'll get hurt'. Just remember the second half must be bad news. -다가는 is never used for a good outcome; that is what makes it sound like love disguised as a scolding.