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

Here is Why You Need An Adapter

The outlet and plug type used in Tajikistan are C and F 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

Tajikistan

In Tajikistan, outlets of type C and F are in use.

Type C

Type F