A Debt Paid Back In Blood

Part One

This was supposed to be a oneshot but since it came out super long I'll be splitting into parts.

Tanjirou knew something was wrong the second the smell hit him, well two smells to be exact. He'd been walking along the edge of the Butterly Mansion, he had just gotten back from a mission while only suffered a minor fracture in his left arm still had to wait until he'd recovered from it to take on more missions. So to get out of the way he'd left Nezuko in her room and decided to take a nice stroll around the grounds while the sun was still up. He'd been stopped when he'd smelt something very distressing, it was a demon but there seemed to be another scent. It smelled of a human that seemed to be calm for the most part but was dangerously close to the former scent. On instinct Tanjirou immediately ran off into the nearby woods towards the scent with a million scenarios running through his mind.

He was scared he wouldn't make it in time to warn the human. What if he'd arrived but the demon had already gotten to them? Shaking his head and drawing a steadying breath he pushed himself to go even faster and began to approach a small clearing in the woods, Tanjirou broke from the treeline and immediately looked around for the threat. It should be around here somewhere, he could still smell it. If it hadn't been for his paranoia he might have noticed that the scent belonging to the demon wasn't exactly hostile.

The young teen glanced around the clearing with his hand hovering over his hip but when he moved to grab the hilt of his sword he noticed that he didn't have it. Tanjirou silently cursed himself but continued to move through the clearing scanning for any oncoming threats but stopped short when he made eye contact with a small boy that was crouched down by a tree and seemed to be peering into a hole in the trunk. The boy was faced away from him so Tanjirou couldn't see his face, the smaller male wore a light green informal kimono but didn't have any shoes on his feet. He was muttering soft words into the hole much to Tanjirou's confusion, but as the demon slayer got closer he realized the demon's scent was coming from the hole.

"Get away from there!" He shouted making the boy jump and turn his head to quickly face him. Now that he was facing him Tanjirou could see that he had black spiky hair that stood up unnaturally and wide hazel brown eyes that narrowed when he set his sights on Tanjirou. "It's unsafe. That's not an animal in there, it's a demon!" Tanjriou called out but was surprised when the boy still didn't move and instead spread his arms and bent his knees in a protective stance in front of where the creature is hiding. The boy was glaring at him now, his lips pressed into a straight line a determination glinting in his amber eyes.

"You guys don't know when to give up, do you?" He spoke lowly as he lowered himself further and he grabbed something from inside the hole. "I told you guys before," Tanjirou tense as the boy pulled a sword from its sheath that had been hidden in the hole as well as the demon, the older male mentally cursed himself for forgetting his own weapon but lowered into a fighting stance nonetheless. "Killua isn't like them!" The boy shouted and held his sword in front of him, Tanjirou half expected him to hold it like any other child his age would when playing with a long stick but this boy held it just as his teacher did.

He held it with the intent to kill.

"I'll give one chance to leave us alone," The boy spat and clutched the sword's hilt tighter.

"Please you have to understand-"

"I don't have to understand anything!" The boy interrupted Tanjirou snapped his mouth shut the boy's eyes were still glaring deep into his own but now they seemed glassy with unshed tears. "I tried to get him help but those guys just told me to give up on him! They told me..." The boy closed his eyes tightly to hold back his oncoming tears but to no avail, they slid slickly down his reddened cheeks and dripped from the point of his chin. "They said he'd have to be killed!" He screamed and Tanjirou faltered, his hands lowered while his eyes widened and stared at the boy in shock. The boy brought a hand to scrub at his eyes roughly as if ashamed of his tears before holding the sword with both hands again. "I tried to get him help, but none of the doctors would come near him! So I went to find a demon slayer but they tried to kill him!" Tanjirou felt tears well up in his eyes as well the more the boy spoke but quickly blinked them away. He couldn't help but wonder if this was how Giyuu felt when he had pleaded for him to spare his sister's life.