This is a guide to unlocking all 31 endings (4 True Endings, 27 Bad Endings) in Sound of Drop -fall into poison-.

As a general rule, the color of the choice buttons tells you how your choice will affect the game:

• Blue background: The choice will have little effect after the current scene.
  
• Red background: The choice can lead to a Bad Ending.

Choices of both types can affect which True Ending you recieve, so check the ending you're aiming for to see which choice(s) you need to make.

Note: The endings are listed in the order they appear on the Ending List.

Common Route

• The first few choices do not seem to have any effect.
  
• "Going back is dangerous... I can't do anything by stopping here... I have to press on."
  
• "No... I can't think of anything..."
  
• Choose any option.
  
• "Please wait, I'll go."
  
• "We should get a better look."
  
• "Kick about frantically.", or "Call out frantically." then "Kick about frantically."
  
• Choose either option.
  
• "Look for a way out of the aquarium."
  
• "Go back using a new route."
  
• "I have to save her."
  
• "I wonder if I can move the machines with a computer."
  
• "Use its sense of hearing."
  
• Choose either option.
  
• See -Himeno- or -Princess of drops-.

New Game+ Route
To unlock an expanded introduction scene about Miku, complete either -Himeno- or -Princess of drops-, then start a new game. Viewing this scene unlocks a new route later in the game. Most of the new endings added to the Steam version of Sound of Drop are found on this route. (To remain on the original common route, choose "Kick about frantically." during the scene with Kenji.)

• The first few choices do not seem to have any effect.
  
• "Going back is dangerous... I can't do anything by stopping here... I have to press on."
  
• "No... I can't think of anything..."
  
• Choose any option.
  
• "Please wait, I'll go."
  
• "We should get a better look."
  
• "Call out frantically."
  
• "Even so, call his name."
  
• "Kenji." This choice is only unlocked if you saw the Miku opening on this playthough. (Saves from a first playthrough will not have this choice available.)
  
• Choose either option.
  
• "Look for a way out of the aquarium."
  
• Choose either option.
  
• "I have to save her."
  
• "I wonder if I can move the machines with a computer."
  
• "Use its sense of hearing."
  
• Choose either option.
  
• Choose either option.
  
• "No, I should stop."
  
• Choose either option.
  
• Choose either option.
  
• "Run straight through."
  
• "Move on."
  
• Choose either option.
  
• Choose either option.
  
• See -the limited ocean of the life- or -fall into poison-.

-Himeno-

• "I have to save Mari."
  
• "No, I should stop."
  
• Choose either option.
  
• Choose either option.
  
• "Run straight through."
  
• "Move on."
  
• Choose either option.
  
• "... Wait."
  
• "No, this isn't right."
  
• The choices here disappear when selecting the "wrong" options, but the final answer is "The director's office."
  
• "Stick around."
  
• Choose either option.
  
• "Reach on top of the desk." or "Reach for my pocket."
  
• "Head for the Deep-sea Fish booth."
  
• Choose either option.
  
• "Take the hand."
  
• "Pull Mari back."
  
• "I... have no doubts."

-Princess of drops-

• "I have to save Himeno."
  
• "No, I should stop."
  
• Choose either option.
  
• Choose either option.
  
• "Run straight through."
  
• "Move on."
  
• Choose either option.
  
• "... Wait."
  
• "No, this isn't right."
  
• The choices here disappear when selecting the "wrong" options, but the final answer is "The director's office."
  
• "Stick around."
  
• Choose either option.
  
• "Reach on top of the desk." or "Reach for my pocket."
  
• "Head for the Deep-sea Fish booth."
  
• Choose either option.
  
• "Take the hand."
  
• "Pull Mari back."
  
• "I... have no doubts."

-the limited ocean of the life-

• "Go with Kenji-san."
  
• "Pull Mari close and protect her."
  
• Choose either option, then choose the opposite option.

-fall into poison-

• "I'll stay here with her."
  
• Choose either option.
  
• "If that's what you really want, Mari, I'll--"
  
• The game will pretend to give you Bad Ending 27 "The Marionette Won't Laugh". Don't reload or close the game, clicking to continue from the Bad Ending screen. (This grants Bad Ending 27 if you don't already have it.)

Trivia

• -the limited ocean of the life- and -fall into poison- were added for the Steam release of Sound of Drop.
  
• -Princess of drops- was listed as the good ending in the original version of Sound of Drop, while -Himeno- was listed as the normal ending.

Into the Silent Abyss

• Choose "I feel worried about Himeno all of a sudden. I'll go back."

My Form

• Choose "I have no choice but to run straight through!"

Decapitation One

• Choose "Please, Hiyoshi-san."

Decapitation Two

• Choose "At any rate, let's head inside."

The Tragedy of Helplessness

• Choose "Shake off his right hand."
  
• [Alternate] Choose "Call out frantically.", then "Shake of his right hand."

Is That... Love?

• Choose "Stay with her like this."

Irrational

• Choose "Go back the way I came."

A Neck Smashed by Teeth

• Choose "I have to hurry along."

Melting

• Choose "There's a fire extinguisher."

Chains of Dissent

• Choose "At any rate, I have to get her away from the orca."

Earth-Shattering

• Choose "Use its sense of pain." or "Use its sense of smell."

The Future of the Reckless

• Choose "OK, I'll try it."

The Madness that Follows Indecision

• Choose "Go around."

A Coward's End

• Choose "Go back."

A Blessed Form One

• Choose "Take Mari's Hand."

A Blessed Form Two

• Choose "Okay, I'll go."

Amongst the Gears One

• Choose "Leave the room."

Amongst the Gears Two

• Choose "Reach out for the bookshelf."

Amongst the Gears Three

• Choose "Reach for the door."

Where Salvation Lies

• Choose "Return to Himeno's side."

Deep Mystery

• Choose "Push away the hand."

True Feelings

• Choose "Maybe I... really hate Himeno too."

Misguided

• Choose "Call out frantically.", then "Even so, call his name.", then either "Shinji." or "Kanji."

The Final Stage of Destiny

• Choose "Push Mari away and run."

Forever Cloudy One

• Choose "Go save Mari." then "Go save Mari."

Forever Cloudy Two

• Choose "Save Sayo." then "Save Sayo."

The Marionette Won't Laugh

• Choose "Thank you for everything up to now. And from here on--"

Trivia

• Bad Endings 11, 13, 19, and 24-27 were added for the Steam release of Sound of Drop. (The choices leading to Bad Endings 11 and 19 were alternate methods to acquire other bad endings in the original version.)
  
• Bad Ending 20 "Where Salvation Lies" was listed with the True Endings in the original version of Sound of Drop and played the credits sequence instead of a Bad Ending screen. However, it was still listed as the bad ending in its ending list image.

As of November 10th, 2015, Sound of Drop now has Steam achievements. Most of these are completion achievements that will unlock automatically if you start up a game with all endings and CGs unlocked, but some of them require specific actions to unlock. Since the hints given in the achievement descriptions are really vague, I decided to include a mini-guide on how to get these special achievements.

Welcome to Manten Aquarium

• Start a new game.

To the depths

• Finish the first part of the game (about up to where the first bad ending choice is).

Memories

• Open the CG Gallery.

Traces of the girl

• Open the Ending List.

Something I want to confirm

• Open the message log while in a game.

Scenes that remain in your heart

• Hide the message window while in a game. ("Graphic" button.)

I can't take it anymore!

• Press Alt+F4 while on a Bad Ending screen. (You don't have to click exit, the achievement will pop as the confirmation window appears.)

A strong faith

• Start a new game and make the following choices. (The New Game+ route must be available.)
  
• "...I'm not."
  
• "Was it... hitting on someone?"
  
• "...That's fine."
  
• Enter the New Game+ route.
  
• "Go back the way I came."
  
• "It's Kenji-san."
  
• "That's because... I thought it best."
  
• "Go with Kenji-san."