Then I asked him can you kindly explain what the four nations are?

 He told me, ‘so I have to explain you from the very first’.

Huh?

 Once upon a time there was an old man named Rin he was old and wise.

 He is said to be the god of assassin.

He had two sons named hiroto and taishi. The two brothers were like an invincible pair.

 They loved each other more than their lives but as they grew big their relation was starting to get bad and they both chose different paths.

 The elder brother founded the village named diamond

And

 the little brother founded the village named hearts.