Lesson notes · ≈ JLPT N2 · Intermediate 2
〜のことになると・〜のこととなると~ no koto ni naru to / ~ no koto to naru to
when it comes to
Use 「〜のことになると」 when a particular topic brings out someone’s unusual reaction.
How it works

Why has the same person’s expression changed? As soon as money comes up, he reacts differently from usual.

Put the specific topic first: noun + のことになると. Then describe the unusual reaction.

のこととなると also means that when a certain matter comes up, someone reacts differently from usual.

In the pronunciation example, he loses confidence when pronunciation comes up. The change can be negative, too.

In the money example, 「目の色が変わる」 means a change in expression or attitude, not a literal change in eye color.
