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

Here is Why You Need An Adapter

The outlet and plug type used in Japan are A and B and in Andorra are C and F. This is how they look like.

Andorra

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

Type C

Type F

Japan

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

Type A

Type B