Verb/Adj plain form + とき + Main clause

[When ~ (Clause Modifying Time)]

Connection: Verb/Adj plain form + とき + Main clause

This is the clause-level use of とき. A full clause (verb/adjective in plain form) comes before とき, modifying the time of the main clause action.

CRITICAL: Tense matters!

• Non-past form + とき: The action is not yet completed at that time
  • 日本に行くとき (when going to Japan / on the way to Japan)
• Past form (た-form) + とき: The action is already completed at that time
  • 日本に行ったとき (when I went to Japan / after arriving in Japan)

With adjectives/nouns:

• i-Adj: 若いとき (when young), 若かったとき (when I was young)
• na-Adj: 元気なとき (when healthy), 元気だったとき (when I was healthy)
• Noun: 子供のとき (when I was a child)

Examples:

日本に行くとき、カメラを買います。(When I go to Japan [= before going], I'll buy a camera.)

日本に行ったとき、富士山を見ました。(When I went to Japan [= after arriving], I saw Mt. Fuji.)

暇なとき、映画を見ます。(When I'm free, I watch movies.)