You and Genya were both Demon Slayers, and even good friends, following each other on every mission and training together 24/7.

So naturally, when you both received words from your Kasugai Crow, that you had to follow them ASAP to Master Ubuyashiki’s mansion, you went together. God was that a bad idea..

Once you arrived, it was like all hell broke loose. The mansion had been blown up, leaving nothing but a mushroom cloud of smoke and fire behind—and in the centre of it all was none other than Muzan Kibutsuji, the Demon King.

He was being temporarily held back by Lady Tamayo, while the Hashira, Tanjiro, and you two, took the chance to attack him. But before anyone could land a clear hit, gates opened beneath everyone, sending you all pelting downwards at full speed.

You looked around, millions of rooms, platforms, and pillars forming around you, as large gusts of winds continued to carry you down.

Once you an Genya landed, you quickly established this brand new dimension as the Infinity Castle, filled with millions of demons, all with one mission. End the Demon Slayer Corps once and for all.

You and Genya had been running around for what felt like hours, occasionally having to shoot or slice a demons head off.

You guys soon walked through one of those thousands of halls, before coming across two large doors—Genya went ahead of you, peering inside.

In the room was a tall demon, Uppermoon One, or Kokushibo.. he had Muichiro, the Mist Hashira, pinned up against a pillar with a sword in his shoulder.

Genya quickly pulled out his shotgun, cocking it back and aiming it at Kokushibo, but before he could he was suddenly cut in half at the stomach, collapsing to the floor.

Your eyes widened, but your body didn’t move. You stared at them both in shock and fear, before Sanemi, the Wind Hashira, and Gyomei, the Stone Hashira, appeared, sending series of attacks at Kokushibo.

You took the opportunity to run to Genya, tears in your eyes as you watched the blood slowly seep from his wound.

“His… hair.. get me his hair..” Genya mumbled, his voice hoarse and barely audible.

You nodded, looking for an opening before running forward and grabbing a piece of Kokushibo’s hair that had been cut off between the multiple blows the two hashiras were hitting him with.

You ran back to Genya, holding the hair in your hand,

“Feed it to me…” He exhaled, a significant drop in his voice from before.

You slowly placed the hair between his teeth, watching him swallow it. Your gut churned in disgust.

Before you could react any further, a red mark slowly began to appear on his forehead, one almost identical to Tanjiro’s.

Seconds later, his eye whites turned red, and his eye color changed from purple to Yellow—looking almost identical to the UpperMoon they were stuck fighting.

His body soon reattached itself, allowing him to stand up. He cocked back his gun, which now had a pattern on it as he aimed it at Kokushibo. Signifying the start of yours and his fight against an Uppermoon.