Here are various plots to IY/YYH crossovers that I don't have time to write. Please feel free to use these outlines to write your own story. Make sure to message me so I can read what you come up with.

Kagome hides her shards with the spirit detectives in her onw era, out of Naraku's reach.

The spirit detectives are kagome's protectors on her side of the well. Near the end of her journey when the only shards left are hers and Naraku's she gives her shards to the spirit detectives to take care of. Kagome then goes back in time for longer than expected. Everyone is worried. They search spirit world files to find what happened but are unsuccessful. Naraku shows up in the modern time. He lies to them and says Kagome died 500 years ago. He tries to get the shards. Kagome comes back from the well and saves the day.

timeline: When there are no shards left besides hers and naraku's she leaves her part of the jewel in the future. in the last battle he captures her and gets the information out of her that the shards are in the future. He thinks he kills kagome and inuyasha but they survive. naraku waits 500 years, splitting himself into many lesser demons able to stay in ningenkai until the time is right. The spirit detectives are formed to kill these demons, unaware that they are all one being. Once it comes to the time naraku thinks kagome has finally died in the past, he converges his body together though it is significantly less powerful since the detectives have taken out many parts of him. He attacks the detectives for the jewels they possess and tells them that their dear kagome died 500 years ago. The detectives are distraught but fight to avenge her. Then, kagome and inuyasha arrive injured but alive. with their help, they defeat naraku once and for all. unfortunately, now neither inuyasha or kagome can return to the past for fear of alerting naraku of their survival.