Thunderclap and Flash (a kimetsu no yaiba x Boboiboy crossover)

Frozen

Halintar ran as fast as possible, carrying the only survivor. The 20 cm deep snow, buried the road, making it hard. But he drove on even when his entire body felt like lead. Thorn was the only survivor, he can still be saved.
"Hold on, Thorn." whispered Halilintar, his voice carried by the roar of the wind. He had to keep running even though his feet screamed in pain and his breath choked. Every second, Thorn struggled with death and every second can determine between life and death. Halintar must—

Suddenly, his feet slipped on snow and fell. Thorn bounced off his sling somewhere. Luckily the heavy snow softened the fall. Halintar lost consciousness several minutes before he slowly opening his eyes. He lay on his back among the dry trees without leaves. The sky was very cloudy with a thick cloud coat. Snow soaked his black-red kimono with ice water. His back and head felt sore, but he ignored. There is something very important. Halintar gasped.

"Thorn!"Halintar shouted in panic. He tried to wake up, his body still aching. Halintar looked around nervously, fear struck the heart. Thorn, Thorn, Thorn— Halintar saw his younger brother, a few feet from where he lay. Thorn stood wobbly, his head bowed deeply. His old green kimono was disheveled, stained with dried blood.
"Thorn, don't stand! I'll —"
"RAAAARRHH!" His brother's face frowned in terror. His eyes were wild, staring at Halintar as if hating. He then galloped with his mouth open, fangs pointed and claws as sharp as a mountain lion. Hali stared in disbelief. No way, this can't be his brother!

Halintar was unable to move. His eyes glued to the his creepy brother, who prepared to pounce on him. What should he do? Hit his brother? Impossible!

Just before Thorn stuck his fangs and nails into Halintar, he was suddenly stopped.
Halintar watched the Thorn's sharp claws held a few inches from his face. His face was contorted in an expression as though he was holding something very heavy. He was moved to tears, looked very apologetic and begged his brother. Lightning struck in place. Whatever it is, Thorn struggled against himself. He did not lose his identity. "Thorn, don't lose! Thorn!" called Lightning.

Thorn closed his eyes tightly. He growled in frustration, suddenly biting his own arm. He continued growling as he buried his fangs in his hands, the blood streaming down the white snow. He knelt before Halintar and curled up in the snow, his body shaking violently. Halintar came to his knees, touching his brother's shoulder.
"...Thorn?"

"Get away from him!" someone shouted. Halintar turned around. There, an adult woman dressed in a black uniform and a bright red haori not far from Halilintar, raised her katana as if ready to cut. The sword glowed a yellowish golden color.