Complex sentence: She remained in Tokyo through the great fire-bombing of March 9,1945, during which she was sheltered with other family members in a special bunker in the Azabu district of Tokyo, far from the heavy bombing.
Split into simpler sentences: She remained in Tokyo through the great fire-bombing of March 9,1945. During the fire-bombing, she was sheltered with other members of her family in a special bunker in the Azabu district of Tokyo, far from the heavy bombing.