You Do Need power plug adapter while traveling from Japan to Falkland Islands.

Here is Why You Need An Adapter

The outlet and plug type used in Falkland Islands is G and in Japan are A and B. This is how they look like.

Japan

In Japan, outlets of type A and B are in use.

Type A

Type B

Falkland Islands

In Falkland Islands, outlets of type G are in use.

Type G