An unexpected attack

A week after the fight between Yuuki and Stella, we see several people in the guild chatting until a man sitting at one of the tables next to someone says:

Man 1: "Have you heard about that duo?"

Man 2: "The one with two prodigies?"

Man 1: "Yes, Yuuki and Stella."

Man 2: "I heard they've already completed over 60 missions in just one week."

Man 1: "I also heard that when they take the Ranking Exam, they're sure to reach the gold ranking."

Man 2: "I've also heard that the two of them together are stronger than some gold-ranked adventurers."

Man 1: "Speak of the devil."

Yuuki and Stella enter through the guild's door. Yuuki is holding the head of a large snake. They both approach the counter where Lility is, and there's a man with an axe arm who looks irritated and is shouting. Yuuki pushes him aside and places the snake's head on the counter. Stella says:

Stella: "Here's the head of the lake serpent."

Yuuki: "This creature was quite a hassle, it wouldn't stop attacking."

Stella: "Indeed, but I managed to freeze its body, and Brat here just decapitated it."

Man: "Hey, do you know who I am?"

Yuuki: "Lility, could you give us our reward?"

Zack: "Don't ignore me; I'm Zack, the axe hand, ranked Iron, 1st place." Zack is a large, bald, muscular man wearing an unbuttoned white shirt, gray shorts with a belt, and instead of his right arm, he has an axe.

Yuuki/Stella: "Never heard of you."

Zack: "You're just a couple of weaklings; your fame must have gone to your heads, but you're nobodies. I'll show you."

Zack attempts to attack them, but Yuuki and Stella both punch him in the stomach and then deliver a blow to his chin. Zack falls to the ground defeated. Lility looks at him and says:

Lility: "That was unnecessary; just the stomach punch would have taken him down."

Yuuki: "Why was he shouting?"

Lility: "He was trying to ask me out, but I declined, and he got irritated."

Stella: "If it were me, I would have punched him already."

Yuuki: "Nothing out of the ordinary."

Stella: "Just be quiet."

Lility: "Anyway, go ahead and take your reward." Lility places some coins on the counter.

Yuuki: "Thank you."

Lility: "Now, go get another mission."

Yuuki: "Alright."

Lility: "Wait a moment."

Stella: "Yes?"

Lility: "I have a mission for you two."

Yuuki: "What's it about?"

Lility: "This one." She places a poster on the counter. Yuuki takes the poster, and he and Stella read it. Lility explains, "It's about collecting Red Snake venom bottles. However, this mission is far away in Dungeon C number 7. Despite paying 10 silver coins for each bottle, no one is accepting the mission."

Stella: "How long is the journey?"

Lility: "A three-hour trip one way."

Yuuki: "What do you think, Dragon?"

Stella: "It's fine. I don't have anything else scheduled for today."

Yuuki: "We accept."

Lility: "Perfect. I'll arrange a wagon for you. Wait here; I'll be back shortly."

Yuuki and Stella go to one of the tables and wait. After a few minutes, Lility appears at the door and calls them outside. She presents a wooden wagon with a white cover and two black horses.

Lility: "I've packed enough food and water for two people for about a day and 40 special bottles for collecting venom."

Yuuki: "Perfect."

Lility: "Just head north, and you'll reach the dungeon."

Stella: "Alright, we'll see you later, Lility."

Lility: "Goodbye to both of you; take care."

Yuuki and Stella climb onto the wagon and set off, bidding farewell to Lility. They leave the city and enter a forest after crossing a plain.

Dungeon:

These are large structures with multiple underground floors. Every floor has monsters, and every 10 floors, the monsters become stronger. There is an exception between the floors: every 9th floor is a safe floor where there are no monsters, and it has food and drink. At the end of each dungeon, there is an alpha, a more powerful version of some normal monsters, guarding rooms with treasures, including the possibility of Legendary Arms. The dungeons are numbered by their discovery order and categorized by the difficulty of the monsters on the first 10 floors.

Legendary Arms:

These are weapons forged centuries ago by an ancient race. They are versatile weapons that take the form of the user's most compatible weapon. When not in use, they resemble common items like a ribbon, bracelet, and so on.

Bestiary Moment:

Red Snake:

These are Monster Snakes. Their height and width depend on their strength and age. They have red scales and beige bellies. They can breathe fire and venom. This species has variations based on their elemental affinity, changing the color of their scales accordingly.

After some time on their journey, the duo stops the wagon near a lake for the horses to rest. Yuuki and Stella sit beneath a tree and take a short break. Yuuki eventually asks:

Yuuki: "Dragon, what's your family like?"

Stella: "Can't you think of anything better to ask?"

Yuuki: "I'm sorry; I..."

Stella: "I don't like talking about it much."

Yuuki: "My apologies."

Stella: "What about your family?"

Yuuki: "I don't know. I don't have one. The only thing I have is my brother, but he's very busy, so we don't talk much."

Stella: "I see. Hey, Brat?"

Yuuki: "I'm listening."

Stella: "How did you meet Lility?"

Yuuki: "I met her not long after I joined the guild; she struck up a conversation with me."

Stella: "I see. Well, let's get going with our journey."

Yuuki: "Sure."

The two leave the tree and return to the wagon. They continue their journey to the dungeon, collecting various Red Snake venom bottles along the way. After a while, Stella looks at Yuuki and says:

Stella: "I'm tired. Let's go back home."

Yuuki: "I'm tired too. Let's get out of here. Wait, did you hear that?"

Stella: "Yes." The two stare at the next door and hear the sound of something large crawling. From the dark door emerges a giant snake, much larger than them, with dark red scales. Yuuki, upon seeing the creature, cries out in desperation:

Yuuki: "It's a Titanium Red Snake!"

Stella: "What is a creature like that doing on the first floor?" Stella says in alarm.

Yuuki: "I don't know, but we have to get out of here!"

Bestiary Moment:

Titan

ium:

It's a category of ancient monsters. It occurs when a monster gets older, but instead of weakening, it gets stronger. This happens when a monster consumes over 5000 other monsters throughout its life. When they reach this category, they increase in size, resilience, magical power, and their scales darken.

Yuuki and Stella start running desperately toward the exit. However, the giant snake begins to form a massive fireball in its mouth and hurls it towards them. They manage to dodge the attack, but it destroys the exit, and the impact causes the ground to collapse, and the three fall into the depths of the dungeon.