The sound of crickets and croaking of frogs permeates the silence of the night. A young boy named Seita is washing dishes in the river as he is joined by Setsuko, his little sister. “Stay inside the net. You will get bug bites,” he tells her. “It’s dark and I’m scared,” she whimpers. Seita finds a way to resolve Setsuko’s difficulty. As he asks her to get inside the mosquito net in the cave—their new makeshift home—he opens his palms and releases fireflies inside the net. In a stunningly beautiful scene, the whole cave lights up with the quiet glow of the fireflies. One lands on Setsuko’s hair. “Look! It’s a hairpin,” Seita exclaims gleefully. Next morning, Seita sees Setsuko hunched on the ground, digging the earth. “What’s that?” he asks. “It’s a grave,” she replies. “Mama’s also in a grave, right?” Shock splashes across Seita’s face, as he sees Setsuko put the dead fireflies in the earth pit. Their mother’s burnt body being thrown in a pit full of the dead flashes before his eyes. “Auntie told me. Mama is already dead and in a grave,” Setsuko says solemnly, while burying the fireflies. Tears flood Seita’s eyes. He realises that Setsuko knows about their mother’s death. He tries to comfort her with a promise to visit their mother’s grave. A teary Setsuko looks up, heartbroken, and asks, “Why do fireflies have to die so soon?”