끝까지 널 지킬 거야

The line, explained

Every great chorus needs a promise, and Korean has an ending built for exactly that. 끝까지 널 지킬 거야 — 'I'll protect you till the end'. The grammar is -(으)ㄹ 거야, the casual future tense, and it is less a prediction than a declaration: this is what I am going to do, and you can hold me to it, every single night.

끝까지 opens the line. 끝 means 'end' — the end of a road, a story, a relationship — and 까지 means 'until' or 'up to'. Together they mean 'to the very end', and the word carries a stubbornness that English 'forever' does not quite have. 널 is 너를, 'you' as the object, squeezed into one syllable so the rhythm stays tight. Korean lyrics do this constantly.

지킬 is the verb, and the shape is new. The dictionary form is 지키다, which means 'to protect' or 'to guard', and also 'to keep' as in keeping a promise. To build the future, you take the stem 지키 and add ㄹ underneath the last syllable: 지킬. If the stem ends in a consonant you add 을 instead, so 먹다 (to eat) becomes 먹을. This ㄹ/을 is the future marker, and you will meet it in many other patterns.

거야 finishes the job. It is the casual form of 것이야, 'it is the thing', and in this pattern it just means 'will' or 'going to'. 지킬 거야 is literally 'protect-will thing-is', but you do not need to feel the pieces — just hear it as one unit meaning 'I will protect'. Make it polite with 거예요: 지킬 거예요. Ask about someone's plans with a rising tone: 갈 거야? 'Are you going to go?'

This ending is how Koreans state intentions all day long — 내일 갈 거야 (I'll go tomorrow), 다 먹을 거야 (I'll eat it all). In a song it becomes a vow, which is why swapping the verb changes the whole relationship: 끝까지 널 사랑할 거야 is a love song, 끝까지 널 기억할 거야 is a goodbye, 끝까지 널 믿을 거야 is loyalty under fire. Same promise shape, different heart.