The following guide will give you the steps to unlock some of the achievements that are missable, as well as provide some walkthroughs for the ending achievements.

About the ending achievements (The Truth and Gone), it's possible to get them using various choice combinations, so I am only including an example for each one under the Stormy/Blue Skies guides. Feel free to experiment to see what else works!

About Stormy Skies/Blue Skies, I am not entirely sure if they are only obtainable as Male or Female respectively or if there is a specific gender-choices combination that you need to pick in order to unlock them, but I couldn't trigger the first one as Female, no matter how many times I tried with various combinations. Most of my playthroughs were completed as Female and then I attempted doing the same choices as Male and one of the combinations I had already tried worked. Thus I have presented that particular example. Let me know if something else works!

Stormy/Blue Skies work as both Male and Female with the new update as of June 07,2015.

Mars

A burning fire

When you start the game you are asked if you are going on the adventure as a male or female. Pick male to get this achievement.

Venus

A calming glow

When you start the game you are asked if you are going on the adventure as a male or female. Pick female to get this achievement.

Mesmerised

Captivated by what could be...

A few lines after you begin your adventure you will see a line that reads :
"Mesmerised, lost in the abyss, I had an overwhelming desire to obtain one of these elusive glimmers of light."
Do not press anything and remain in that screen for about 1.5 minute to get the achievement.

Update : According to Crimson Night, you can get this achievement by spending that time overall in the first scene. It doesn't have to be on that exact line. (Thank you for the info!)

Observant

Take note of your surroundings

When you are stuck going in circles in town with Kira and you are presented with a choice, pick the option "I've got the feeling it could be the next left?" and the achievement will unlock.

Taste The Rainbow

Try 2 different milkshakes

When you are out with Kira and she asks you if you like milkshakes, respond with the choice "Hell yeah!". Later she will offer you some of her milkshake and you need to pick the choice "but soldiered through so as not to lose face." to try out some of her milkshake, too and unlock this achievement.

Time Slip

Visit the ancient courtyard

I believe this is a story achievement so you should be able to unlock it naturally by playing the game. It unlocks when you come across the beautiful courtyard.

Darwin

Demonstrate a firm scientific grasp

After swimming along with Kira, while she is talking about the "fish theory" and you are presented with a choice, pick "That sounds like a robust theory to me." to unlock this achievement.

The Truth

Reach ending 1

The "Good Ending". You will naturally reach one of the two endings by playing.

Check the "Blue Skies" part of the guide below for an example of choices that lead you to a good ending. You can, obviously, get to the good ending by various other choices as well, thus I am only presenting an example.

Gone

Reach ending 2

The "Bad Ending". You will naturally reach one of the two endings by playing.

Check the "Stormy Skies part of the guide below for an example of choices that lead you to a bad ending. You can, obviously, get to the bad ending by various other choices as well, thus I am only presenting an example.

Stormy Skies

Alienate yourself from Kira as much as possible

This is a bad ending.

NOTICE (November 5, 2016) : I cannot test the following but according to the developer "When you're asked whether you heard the owl's call or not - your answer to that question never effected which ending you got."

I'm including this here since I cannot verify it, because I already have the achievements now. If someone wants to let me know of their results, feel free to comment!

You get this achievement when the credits start so make sure you finish the playthrough. I didn't notice any particular change between this and the Gone ending except for the achievement popping up during the credits so I am unsure if a particular gender-choice combination triggers the achievement or if there are various ones you can pick. The problem I had was that I kept trying my playthroughs as a Female and writing them down so as not to repeat them. After a while, I started retrying them as a Male (since I ran out of ideas) and got the achievement, so there is a chance this achievement is gender specific. UPDATE : The achievement now works as either Female or Male. If someone can try these as a Female before trying as a Male to verify it was not just an error on my side, I would appreciate the info. Also, if someone triggers this achievement with another combination, I would be interested to know what it was.

So here are the choices :

- Male or Female (This choice does not matter any more, the update fixed that.)
- Trying to avoid eye contact with her.
- I squeaked.
- Guess.
- I've got the feeling it could be the next left?
- Find out more about the bracelet.
- ...I'm lactose intolerant.
- Most people think it's a regular squid, I'm impressed you know the difference!
- It's a part of the human psyche, something that can't be helped.
- If you really mean that, then no I wouldn't.
- Yes.
- I agree.
- Meekly do as you're told.
- I'm not sure it's a great idea...
- That sounds like a robust theory to me. (This choice was just changed with the new update, the other one used to get you to Stormy Skies before)

And proceed to the end to get the achievement (don't stop before the credits start).

Blue Skies

Endear yourself to Kira as much as possible

This is a good ending.

NOTICE (November 5, 2016) : I cannot test the following but according to the developer "When you're asked whether you heard the owl's call or not - your answer to that question never effected which ending you got."

I'm including this here since I cannot verify it, because I already have the achievements now. If someone wants to let me know of their results, feel free to comment!

After finding Blue Skies, this one was easier to track down, as I just picked the opposite choices. This time I tried playing as Female first to check if it's specific to Male like the other one seemed to be, but the achievement unlocked so I cannot test if it's Female only or not, now. UPDATE : Both users and dev verified that the achievement works for both Male and Female. If someone tries this choice combination as Male, please let me know if the achievement triggered. Also, let me know if you unlock it with another combination.

I also didn't notice any difference between this and any general The Truth ending, so I am unsure what the exact difference is.

So here are the choices :

- Male or Female (This choice doesn't matter.)
- Nervously grinning whenever she looked in my direction.
- I boomed confidently.
- Succumb.
- ..I left her to it though as I didn't mind where we were, I was enjoying her company.
- Scour the floor for it.
- Hell yeah!
- but soldiered through so as not to lose face. (Unsure if this affects anything since it doesn't pop up in the opposite choice.)
- It is indeed!
- Just because someone gravitates more easily towards a certain behaviour doesn't make it right.
- Yes.
- No.
- I disagree.
- Throw down the bread roll and leg it to the water.
- Of course.
- Oh, and you believe the rest? (This choice was just changed with the new update, the other one used to get you to Blue Skies before)

And proceed to the end to get the achievement (don't stop before the credits start).

Columbus

Travel to an undiscovered land

While on the main menu, click on Kira's bracelet for a little secret and this achievement!

A hint on how to unlock this one shows up after you finish the game sometimes, as advice from Grant, so I am not sure if you need to have finished the game to have access to that secret or not, since I found it after I had finished the game and saw the hint.

Thank you for reading this guide!

I appreciate the feedback so feel free to comment, especially if you find any errors (I might have made a few mistakes while trying to format this)!

I'd also like to thank Crimson Night, both for making this game and for verifying some of the info in this guide!

Change Log :
June 7, 2015 : Updated the Stormy/Blue Skies guide since the old choices did not work with the new update. Updated the time for Mesmerised to 1.5 min. (Thank you, Deiru Capulet and Crimson Night for confirming).
November 5, 2016 : Added info from the developer on Stormy Skies and Blue Skies. If you have any problems getting those achievements, please read the notice.