The Sewers
The Sewer is the first part of the Prologue, in him, you can learn the basic things to start playing Die Young (movement, climbing, combat, crafting, etc...)
Contents
The Start
Daphne starts in a sewer where she can't escape because there are two dogs guarding the entrance, she only has one possible thing to do, start walk for a mysterious and unknown sewer, with (for the start) only one lighter.
The first mission added to the Quest menu is "Escape the Island - Find the Exit of the Sewers".
The Lighter
There is one lighter in front of Daphne when the game starts. Taking the Lighter allows the player to illuminate zones without light (or reduced light).
The First Jump
After walking for the first Sewer you find the first jump (with tutorial).
You can easily jump just pressing the Jump button (Controls).
The First Weapon
After climbing the first spot you can find your first weapon, is a Wooden Stick (Weapons) and can be useful to kill small enemies.
The First Enemies
After taking the Wooden Stick you can find your first enemies, they are Rats, they are small, has low health and do low damage but they can encounter in big groups and can suppose a big problem if you don't kill them fast.
Ladders
After crouching and walking for a sewer, you can find the first ladders, to climb it, just press the Jump button (Controls) when you see the next indicator. 
Kidnapped
In the Sewers you can find a human that looks like another kidnapped (like Daphne), anyway, you can't reach him.
The First Document
In one wall you can find the first document, there are a lot of documents in the game and you can find them sparsed in the map.
The first document is called "Escape Route" and is a map to escape from the Sewers (and with another marked spot).
The First Medkit
You can find the first Medkit in one wall of the Sewers.
One Medkit fully restores Health and heals all statuses. (Consumables)
The First climbing spot
In the Sewers, you can also find the first Climbing spot tutorial. To climb it, just press the Jump button (Controls) when you see the climb indicator.
You can press the button for "Use Perception" (Controls) to highlight all possible climb spots.
The Exit 4
The Exit 4 (that is shown in the first document) is a door locked and can't be unlocked.
You need to find another way to escape from the Sewers.
The First Crowbar & Padlocks
The Crowbar is a weapon (Weapons) that can be used as a tool to unlock some doors locked with padlocks. In this case, you can unlock the door of the left side from the site you found the Crowbar (and can be useful for the future too).
Padlocks can be unlocked with Crowbar holding the "Attack/Use item" button in it
Molotovs
You can easily make Molotovs in the containers with fuel. Hold the "Canteen" button (Controls) (with Empty Bottles in the inventory) to make it.
Molotovs can be useful to kill groups of enemies like Rats (throw the Molotovs using the "Throw" button (Controls).
The First Human Enemy
In the Sewers, you can find to the first Human enemy, in this case, a "Junk" enemy.
Human enemies are strongest than the animals and have more attacks (like throwing rocks, jump+attack, evade).
The Final of the Sewers
After killing (or evading) the human enemy, you can find the final of the Sewers, after passing for the exit starts the second Quest "Go past the Harbor".
