Why didn't Itachi use Kotoamatsukami on Obito rather than save it for Sasuke?
Like Itachi decided to die by Sasuke's hand, so that Sasuke would return to the village and protect it, but then kept Kotoamatsukami as a backup plan in case Sasuke found out the truth about Itachi and decided to destroy the village. He was also worried about Obito getting to Sasuke first and telling him the truth so he implanted a timed Amaterasu attack into Sasuke's eye in an attempt to kill Obito should the two ever meet, this ofcourse didn't work. So why didn't Itachi instead use Kotoamatsukami against Obito from the very beginning, then die by Sasuke as originally planned, then Sasuke would go back to the village, Obito could have also returned to the village theoretically, and the War would have never happened, and the village would be safer than ever.
Like Itachi decided to die by Sasuke's hand, so that Sasuke would return to the village and protect it, but then kept Kotoamatsukami as a backup plan in case Sasuke found out the truth about Itachi and decided to destroy the village. He was also worried about Obito getting to Sasuke first and telling him the truth so he implanted a timed Amaterasu attack into Sasuke's eye in an attempt to kill Obito should the two ever meet, this ofcourse didn't work. So why didn't Itachi instead use Kotoamatsukami against Obito from the very beginning, then die by Sasuke as originally planned, then Sasuke would go back to the village, Obito could have also returned to the village theoretically, and the War would have never happened, and the village would be safer than ever.