Explaining the story ~ cr. Whoever wrote it (not mine)

Yuzuru's mother got pregnant in October when the Gods leave and Yokais (demons) attack. So, Yuzuru is half yokai, half human. When the mother married the father, they had a twin, Ayato and Takumi. However, to prevent Yuzuru from becoming a yokai, the father bargained with the Gods to replace Yuzuru and became a yokai himself. He lived in the shrine with the twin (he won't hurt them as they are his own sons) while the mother lived a normal life with Yuzuru. However, Ayato went to school and meet Yuzuru and fell in love. The father on the other hand attacked and ate all those who hurt Yuzuru as a way of protecting him. When Yuzuru realized that all those who died were the ones he had a bit of confict with, he decided to go to the shrine to talk to the Gods. Since Yuzuru is already a human and he is not related by blood to the father, he attacked him. ButAyato saved him and sacrificed his life. Upin realizing that it was his own son that he ate, the father then burned himself to death. Yuzuru had an amnesia because of the trauma this event brought him and forgot all of what happened. His mother re-married Ryosuke's father and lived normally in a different town. However, Ayato's twin Takumi followed them and watched while Yuzuru grew up. At first, his intention was to take revenge. But he slowly fell in love with Yuzuru and decided to make him fall for him too. He locked Yuzuru up to ensure that he will not end up eating humans when time comes that he will turn into a yokai. Yuzuru will still become a yokai upon adulthood because the replacement, the father, died. Not realizing this and only remembering the past, Yuzuru decided to set himself on fire to atone the sin (he felt guilty of the death of the father and Ayato and for making Takumi lonely). When he wouldn't burn to death, he realized that he is the yokai. He wanted to live alone in the shrine and starve to death but Takumi wouldn't let him. Since they love each other, they decided to kill themselves at the train station by jumping in the railway while a train is approachibg. The graves were probably made by Ryosuke and Takumi's friend. When the kid saw them at the shrine, its already their spirits.