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

Yellow Lightning

Halintar were still, his eyes fixed on Thorn. His brother stared back at him, regret filling his emerald green eye as he cried silently as if in torture. Halilintar's chest hurt seeing his brother's suffering.

thorn is still thorn, even though he changed.
He is still Halilintar's little brother! Halintar pulled out his dagger, his eyes glistening with rage.
"Even though he's not human, I'll will protect him!"
"How?" said the woman with a mocking laugh. "Your brother will only eat innocent humans thanks to you!"
"He won't and I will cure him!" shouted Halilintar. He tightened his dagger grip. "Now leave him alone!"

Desperate and angry, Halilintar ran toward the woman, his hand holding the dagger. The woman just sighed tiredly, unphased by his attack.
"You don't know anything," She grumbled, kicking hurts in the stomach.
Halilintar fainted immediately from the shock, collapsing into the snow, as the woman breathed a sigh of relief.
"Now, time to finish this demon," She muttered as she grabbed Thorn's hair, ready to kill. But when she was about to swing her katana, she realized something.
The demon had chewed his own arm until the flesh was torn off, blood seeping the snow under his feet. His ferocious face was in pain and fear, but not of death...or her.

She didn't understand, her katana was pressed against on Thorn's neck yet this demon restrained itself by biting its own arm and didn't struggle at all. He did not even care about the sword drawn at his neck, his eyes gazing sadly at his brother who was collapsed unconscious. The strangest thing was this demon was crying, an emotional activity. No demons cry. They were wild animals. Eat, eat, eat and survive. They did not cry sadly like Thorn. They didn't look sadly at his brother that he should have eaten. Maybe, just maybe this demon can be heal again. Maybe there is a way.

Halilintar awakes up with cramps. His eyes opened slowly, seeing the woman standing close to him. He jumped on his feet, ready to protect his brother once again.

"Don't panic," said the woman, reading the chaos of the Lightning. "I'm not going to kill him." Halilintar did not answer, but stared at the woman with both astonishment and hope. The woman knelt by his side and pointed to the right of Halilintar. The teenager turned and saw Thorn lying unconscious, his mouth tied up with a stick of bamboo. He looks peaceful as if nothing happened. relieved, he patted Duri's cheek as if making sure his brother was safe. "Why did you let him go?" asked Halilintar, confused. "Who are you?"

"My name is Satriantar, Lightning Pillar," he said calmly. "I am a demon hunter. I'm sending you and your brother to my teacher, Kuwajima Jigorou, the former Lightning Pillar, so you can train with him. I have written a letter of recommendation, give it to him."
Hali look dumbfounded. "What?"

A/N
Satriantar: on the BoBoiBoy Galaxy Card, Satriantar was the owner of the Lightning / Halilintar power before it was taken by Retak'ka and moved to BoBoiBoy. She is a woman, not a man, just like Kuputeri, the owner of the Wind / Taufan power.