when it comes to topic A
habit/attitude appears
Open details
Form: N + の + ことに/ことが + なると｜こととなると (more formal)
Use: When topic A is involved, a typical attitude/behavior shows up.
Mini examples
if/once it comes to A → B
result/inference
Open details
Form: N／V-plain + と なると／なれば／なったら
Use: If that situation happens or is true, B follows (decision, plan, guess).
Mini examples
as A changes, B also changes
correlation / parallel change
Open details
Form: N + とともに ／ V-dict + とともに
Use: Two things increase/decrease or change together over time/scope.
Mini examples
1) 〜ことになると・〜こととなると — when it comes to A
Topic A triggers someone’s typical stance or behavior.
Form: N + の + ことに／ことが + なると（こととなると is more formal)
When it’s about safety, we never compromise.
When it comes to my hobbies, I can’t stop talking.
2) 〜となると・〜となれば・〜となったら — if/once it comes to A
Set a condition or situation and draw a plan/judgment.
Form: N／V-plain + と なると／なれば／なったら
If taxes go up, I’m worried about the household budget.
If it’s officially decided, let’s start preparing at once.
3) 〜とともに（相関関係） — as A, so B
Show two changes happening together (increase/decrease, spread, aging, etc.).
Form: N + とともに ／ V-dict + とともに
As the population ages, medical needs are rising.
As technology advances, ways of working have changed.
Quick contrasts & pitfalls
- 〜ことになると = “when it’s about A, (habit/attitude)”. Not conditional; it introduces a topic.
- 〜となると／なれば／なったら = conditional step → make a plan/guess. Often used in decisions and news-style logic.
- 〜とともに (correlation) = parallel change over time/scope. Don’t confuse with “together with (accompany)” sense when it means “with someone”.
