Hell's Demon Slayers

5-4: LEVIATHAN

Being the first to fall down, Obanai splashed into a pool of water. Looking around, it seemed that the entire start room was partially submerged in water.

"Well, this is different.", Obanai said to himself as he waited for the others to drop down. Something about this made him uneasy, for some reason. Water splashed onto him as the other Hashira dropped down one by one.

"Should've expected that..", Obanai sighed.

"Why is there water here?", Tengen asked, walking toward and facing the start room.

"My best guess is that someone, or something, was the cause of this. And I have a feeling we're about to find out who in a second.", replied Obanai, taking a deep breath as he submerged himself under the water and exited the start room, revealing several rock formations that acted as platforms. Thanks to the water, they could merely float to the next platform instead of actually jumping to it. However, they still had limited breath, so they tried to get to the other side as quickly as possible.

At one moment, when they were halfway done, there was thunder that echoed throughout the murky depths of the sea. A bit unnerving, sure, but nothing too dangerous or terrifying.. well, until the next thunderclap illuminated the silhouette of some sort of creature, resembling a large sea serpent, almost like the creature they saw last level. At the sight, the Hashira looked at each other in an almost synchronized pattern, traces of fear bubbling up deep inside them as they got closer to the already-fading shadow.

At the end of the path was a hydrothermal vent that propelled each and every one of them back to the surface, landing on top of a long, wooden platform, allowing the Hashira to get a breath of fresh air before what was about to come.

"Just to be clear; I'm not the only one who saw that, right?", Muichiro asked, followed by everyone nodding (except for Gyomei).

"Well, that could only mean one thing..", Tengen muttered, as the water behind him bubbled up, almost as if it was on cue. After several seconds, a large, stony sea serpent adorned with multiple sculpted faces along its body, as well as some sort of organism behind the creature's head.

"LEVIATHAN"

It roared at the Hashira, before it retracted its head as a blue glint appeared next to its mouth. Sanemi could see what it was about to do from a mile away.

"WATCH OUT, EVERYONE!"

As everyone quickly got out of the way, the Leviathan followed through with a sharp lunge, piercing the air but hitting no one. Tengen quickly mounted the Leviathan.

"I hope my gut's right about this!", Tengen said as he ran toward the "heart" of the Leviathan.

"Sound Breathing, First Form: Roar!"

As he raised his blades, he slammed them down onto the fleshy organism within an instant, a large explosion following the impact as the heart splurted out streams of blood. The Leviathan roared in pain as it shook its body, soon causing Tengen to fall off the creature and back onto the platform.

"Nngh.. well, that's damage..", Tengen muttered as he got himself up from the ground.

"Let's try attacking this thing from a range this time; like any normal person would.", said Obanai as he took out his Screwdriver Railcannon and aimed it at the heart of the Leviathan. With a pull of the trigger, a drill stuck onto the organism, doing constant damage over time. The Leviathan opened its mouth before firing a severe barrage of hell orbs, which Obanai merely rolled to the right to dodge.

As its attack ended, it submerged itself into the water, before its tail appeared behind the Hashira to deliver a swift high swing, which thankfully everyone ducked under, effectively dodging the blow. The Leviathan then emerged to the side of the Hashira.