You go back to 2005 as in return for your future actions that have destroyed other people's relationships hundreds of times. Now you're back in 2005, where you have to fix everything. And, one more thing, Kurokawa Izana is the key to your future happiness, in another name, is your soul mate. He was just a boy searching for his identity in 2005. Now, save him because a year later he is gone. And remember, if he dies in the Toman-Tenjiku incident, you go back to 2005.