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

Mentor

In winter, the skies are usually covered in thick grey clouds yet today the sun peeked through it. As Thorn walked alongside his brother, he suddenly roared, running back in pain. Hali panicked, chasing after him, afraid that he might attack humans.
But instead, he found him hiding in a small burrow in a hill, irritated and singed.
"You can't get in the sun, can you?" muttered Halintar with pity. Thorn didn't answer but breathed softly, suddenly asleep.

Now, they only travelled at night, passing haunted areas and getting scared by bandits, which Thorn scares back. While Hali suffered through hunger, thirst and the cold, Thorn was unwinded by the extreme air and never ate or drink. But Halilintar still wrapped his younger brother in a thick cloth guessing sleeping was Thorn's way of recovery.

During the long journey and his observations on Thorn, Halilintar began to understand a little bit more about demons. His mother used to tell him stories about devils made of fire while humans were made from earth. Yet Thorn wasn't like the devils in those stories. He guessed that this "human to demon" change was purely just parasites in the human body —  like viruses or bacteria — that eat away at their host, attacking their consciousness. Local people call these sick humans "demons" because of their terrible behavior, such as cannibalism, savagery and loss of identity. Not to mention the appearance of claws, teeth and inhuman strength.

When the news about his family got out, the villagers panicked, leaving the village. They interrogated  Halintar about what it looked liked and if the rumours were true, but when he told them he didn't know, they left him.

But Satriantar said that it is true that a brutal demon stopped by last night and killed all of his family. Thorn managed to survive because of demon blood.

Someone asked about Thorn's fate and why he wasn't there. Halilintar answered for various reasons: "Thorn was hurt and was resting in a room." "He can't be bothered." "He doesn't want to meet anyone." "The massacre was too traumatic for him."

The real reason was because Satriantar forbid Thorn to meet other humans. No one can guarantee how long he can hold his fangs. Thorn is unpredictable and could attack anytime.

Halilintar was still too shocked and found it hard to accept. His mind was foggy and he couldn't think straight. He even doubted that this was true.

Sure, he will miss Taufan's sweet laughter. He will lose Gempa's shadow. He will long for a calming nature like Ice. He will remember Blaze's fiery spirit and he will continue to remember how he and Solar would argue, secretly appreciating each other. What's more, he will remember being together with his mother. He will not forget the warmth when the seven of them and his mother chatted together by the fire.

Having them made Halilintar feel that he was the richest human being in this world, they were the purse of his heart. He had enough. What else did he want from this world?

But no matter how valuable you think something is, there will always be someone who wants it gone.

So quickly that happiness faded away, like soot blowing in the wind from the rickety walls of his house. So quickly they left him and sailed far into the untouched ocean.
But no matter how many people you lose, you have no choice but to go on living.

A/N
This ending was crap. Sorry. I hope you'll keep reading and thanks for the reads!