expression
when it comes to; if it becomes; where ... is concerned
Used to set up a hypothetical or conditional situation, often followed by a statement about what would happen or what one would do in that case. Can be translated as 'when it comes to...', 'if it becomes...', or 'where ... is concerned' depending on context.
いざとなったら、私が責任を取ります。
When it comes down to it, I'll take responsibility.
彼が来ないとなったら、計画を変更しなければならない。
If it turns out he's not coming, we'll have to change the plan.