alright ok heres the deal, we are in an different universe here are some facts that might clear something up
1.this is a little while after the jewel have been finished, kagome wished for everyone to be happy ie. making sesshoumarus father come back and in a way making Serenity show up.
2. Inuyasha and the gang dont really play a major role
3. Queen Serenity mated with Naraku by accedent with a mix up of time she was sent into the future bacially because she lived on the moon a millenna ago. She went to see pluto about the future and ended up falling thoght a portal which ended up being around the same time Onigumo was a bandit, she was taken by force but was found by Lord Sesshoumaru and teken to his home, when Serenity was born she aged faster because of her moon blood(cant remember what they are called) Sesshoumaru and her fall in love and wished to be mated.She was still around when Onigumo turned into Naraku, he knew what would come ahead and sent Queen Serenity into a portal back into the past where she would stay. So serenity had to leave sesshoumaru.
