With no time for tearful reuinons, Kasane explains the present danger to Wakana. According to Wakana, if they want to destroy the Kunad Gate, they have to unravel the entanglements caused by previous time travel. They must travel inside a gate called the Chronos Terminal. Kasane and her team go to Kunad Highay and activated the Red Strings again.
Wakana guides Kasane and Yuito as they unravel entanglements in the Chronos Terminal. they unravel the entanglement created at the OSF hospital, when Ksane met with Yuito 50 years in the future in Suoh, and at the momen of Yakumo's death that they had glimpsed. As they unreavel the last entanglement are surprised that it was Karen who killed Kaumo. Their powers reach their limit before they can process that reality, forcing them to leave the Chronos Terminal.
Before returning to the past, Wakana tells Kasane and Yuito that she must leave because the entanglement caused by her time travel will be erased by her death. After she leaves, the Kunad Gate doesn't go away. From what they saw in the Chronos Terminal, Kasane and her team reason Karen travelled 2,000 years into the past and killed Yakumo to take his place. If that entanglement remains, they need Karen's help to untangle it. Theyt must enter Sumeragi tomb, where Karen-as-Yakumo most likely is, so they contact Kaito through Fubuki.Compendium