In what way do the similarities between the eras of medieval japan and medieval europe merit using the same adjective to describe them?
i don't understand this question, someone me:

The question means find the ways that Japan and Europe had similar governments during Medieval Times. At least that's what I think the question means.

The Samurai owed absolute and total loyalty to their lord and master. If you ever get the chance to see Shogun, you will understand just how complete their loyalty had to be.

Europe on the other hand had knights that defended the feudal lord (the ruler of the castle the knights served) in much the same way.  

The adjective that might be used was feudalism. Its characteristic in both cases  was land for military service.

The correct answer to this open question is the following.

The similarities between the eras of Medieval Japan and Medieval Europe were the following.

In the Middle Ages, most European territories were ruled by Kings. Kings had absolute power over their reigns. Noble people in the Middle Ages had some privileges and were close to the King court. The King only asked for their loyalty and support. The Nobles had property and in their land, peasants worked in exchange for housing and food.

In the case of Medieval Japan, the military men governed the islands. These military men had a name; the Shogun and exerted its power and influence over the Japanese society.