Soichi Kusakabe is Souji and Hiyori's biological father. He was killed and mimicked by a Native Salis Worm. Several years later, just before the Shibuya meteor hit, Tendou encountered him and another Native who had killed and mimicked his mother. In the impact's immediate aftermath, he tried to kill them but was stopped by Hiyori's cries. Moments later, the two Natives were killed by falling rubble.