By which route did you come to Japan?

[Xinfu]

The expected reply:

-Well, I took a flight from Heathrow Airport, flying over India, and arrived in Nagasaki. The route from the UK over the Atlantic to the US over the Pacific is more troublesome and time-consuming.

Is it natural English to ask a question like this to get the above answer?:

-By which route did you come to Japan?

I wrote the expected reply; is it natural English?

[Rusty]

Well, I took a flight from Heathrow Airport, flying over India, and arrived in Nagasaki. The route from the UK over the Atlantic and to the US over the Pacific is more troublesome and time-consuming.

Is it natural English to ask a question like this to get the above answer?

-By which route did you come to Japan?

I wrote the expected reply; is it natural English?Natural English was used and would be understood.
A bit more natural would be:
Which route did you take (to get) to Japan?


Here are more ways to ask the question, using more colloquial English:
How'd you get to Japan?
What route did you take (to get) to Japan?
Which way did you take to Japan?
Which way did you come to Japan?

[Xinfu]

Thank you, Rusty.

I wrote the expected reply; is it natural English? How can I improve it?

[Rusty]

The only change needed in your reply was marked in red. It sounds natural with that change.
The only improvement would be to change 'is more' to 'would be more'.

[Xinfu]

Thank you, Rusty~