Why is it important to know that china is one of japan's closest neighbors?

Its important to know that China is one of Japan's closest neighbors because they have similar backgrounds and much of which comes from Japan came from China at some point in time.

nothing certain is known about what happened, but it seems that the country declined gradually, perhaps due to bad government, or, more likely, due to a series of bad harvests, which resulted in widespread and recurrent famine.