I'm yours to the end.

Similar expression

 ◈ 무슨 일이 있어도 네 편이 되어줄게.

  ▶  I'll be there through thick and thin. (Idiom)

   Dialogue   

A: It's going to be a long war, and we're going to lose

    friends before it's over.

B: Don't worry, my lord. I'm yours to the end, whatever

    the cost.