My Girlfriend is a Mermaid!? – Walkthrough

My Girlfriend is a Mermaid!?
Walkthrough by Badaro, Version 1.1

***** Version History *****

v1.0 - Initial Release (2024/11/05)
v1.1 - Fixed an error with both "Day 6A, Morning (2)" options listed in a few
endings. (2025/01/19)

***** About the game *****

This is a visual novel from studio COSEN. It's a slice-of-life story where a
young man returns to his hometown and finds out that his childhood friend
mysteriously turned into a mermaid.

The Nintendo Switch version was used when writing this guide.

***** Choices *****

These are all the choices available in the game.

Day 2, Morning:

1. Go out with Ion on my back.
2. Use a cart.
3. Go out and abandon Ion.

Day 2, Afternoon:

1. Manage with something in the area.
2. Starve.

Day 3, Morning:

1. Chat in the house.
2. Take a visit to the fields.
3. Secure rations.

Day 4, Morning:

1. Heal up my face.
2. Do mermaid research.
3. Head to the fields.

Day 4, Afternoon:

1. Succumb to my scientifically-sound inquisitive mind.
2. Succumb to my morally-sound sense of ethics.

Day 4, Night:

1. There's definitely a moral dillemma here.
2. Get bent. This present is mine.

Day 5, Morning:

1. Stroll on the country roads.
2. Take a visit to the fields.
3. Do some research on mermaids.

Day 5, Night (1) (depends on prior choices):

1. Give up and sleep.
or
1. Search to see if there's anything more usable around.
2. Give up and sleep.

Day 5, Night (2) (depends on prior choices):

1. ...I don't know.
or
1. ...I don't know.
2. She's losing her memories.

The game splits into path A or B depending on the choices made so far.

Day 6A, Morning (1):

1. Have I done something wrong?
2. What kind of course should I be taking moving forward?
3. What are your thoughts on the words "humans have to link their future with
one another"?
4. So, why did you do that back then?
5. Whatever is is you're trying to do, stop it now!
6. I'm sorry, I was in the wrong.

Day 6A, Morning (2):

1. Talk with Rin-san.
2. Form a hypothesis based on info thus far.

Day 6A, Afternoon:

1. Toss them.
2. Put then back where they were.

Day 6A, Night:

1. I raise my hand with enough force to move the unnecessarily beautiful moon
above.
2. I try to pick a way to reliably save Ion, at the very least.

Day 6B, Morning:

1. Slip into the shrine.
2. Go put Petako in the reservoid.
3. Heal my wounded body.

Day 6B, Afternoon (depends on prior choices):

1. Chat with Ion.
or
1. Chat with Ion.
2. Take a visit to the fields.
or
1. Chat with Ion.
2. Do mermaid research.

***** Endings *****

Bad Ending 1:

1. Go out with Ion on my back.
1. Manage with something in the area.
3. Secure rations.
2. Do mermaid research.
1. Succumb to my scientifically-sound inquisitive mind.
2. Get bent. This present is mine.
1. Stroll on the country roads.
1. Search to see if there's anything more usable around.
2. She's losing her memories.
6. I'm sorry, I was in the wrong.
1. Talk with Rin-san.

Bad Ending 2:

1. Go out with Ion on my back.
1. Manage with something in the area.
3. Secure rations.
2. Do mermaid research.
1. Succumb to my scientifically-sound inquisitive mind.
2. Get bent. This present is mine.
1. Stroll on the country roads.
1. Search to see if there's anything more usable around.
2. She's losing her memories.
6. I'm sorry, I was in the wrong.
2. Form a hypothesis based on info thus far.
2. Put then back where they were.

Bad Ending 3:

1. Go out with Ion on my back.
1. Manage with something in the area.
1. Chat in the house.
1. Heal up my face.
1. Succumb to my scientifically-sound inquisitive mind.
1. There's definitely a moral dillemma here.
1. Stroll on the country roads.
1. Give up and sleep.
1. Slip into the shrine.
1. Chat with Ion.

Bad Ending 4:

2. Use a cart.
1. Manage with something in the area.
2. Take a visit to the fields.
3. Head to the fields.
2. Succumb to my morally-sound sense of ethics.
1. There's definitely a moral dillemma here.
2. Take a visit to the fields.
1. Give up and sleep.
1. Slip into the shrine.
2. Take a visit to the fields.

Bad Ending 5:

3. Go out and abandon Ion.
1. Manage with something in the area.
1. Chat in the house.
2. Do mermaid research.
2. Succumb to my morally-sound sense of ethics.
1. There's definitely a moral dillemma here.
3. Do some research on mermaids.
1. Give up and sleep.
3. Heal my wounded body.
2. Do mermaid research.

Bad Ending 6:

Do NOT make any choices during the entire game. Simply leave the cursor over the
first option and wait for it to timeout.

Good Ending:

1. Go out with Ion on my back.
1. Manage with something in the area.
3. Secure rations.
2. Do mermaid research.
1. Succumb to my scientifically-sound inquisitive mind.
2. Get bent. This present is mine.
1. Stroll on the country roads.
1. Search to see if there's anything more usable around.
2. She's losing her memories.
6. I'm sorry, I was in the wrong.
2. Form a hypothesis based on info thus far.
1. Toss them.
2. I try to pick a way to reliably save Ion, at the very least.

True Ending:

1. Go out with Ion on my back.
1. Manage with something in the area.
3. Secure rations.
2. Do mermaid research.
1. Succumb to my scientifically-sound inquisitive mind.
2. Get bent. This present is mine.
1. Stroll on the country roads.
1. Search to see if there's anything more usable around.
2. She's losing her memories.
6. I'm sorry, I was in the wrong.
2. Form a hypothesis based on info thus far.
1. Toss them.
1. I raise my hand with enough force to move the unnecessarily beautiful moon
above.

You should also get the "Perfect Choices" achievement from these choices.

***** Extra Stories *****

01-12 Unlocked from choices or endings in the main game.
13-15 Unlocked from the extra stories.
16-17 Unlocked from choices or endings in the main game.
18-19 Unlocked from the extra stories.
20-21 Unlocked from choices or endings in the main game.

***** Illustrations *****

01-18 Unlocked from choices or endings in the main game.
19-24 Unlocked from the extra stories.
25-29 Change the console clock to the months of January, February, April, July
and September, then start a new game once for each month.
30-39 Randomly acquired when choosing the "Title" option from in-game menu. You
can load and go back to the title repeatedly to unlock them all.

***** Movies *****

There's four versions of the opening movie, one for each language (English,
Japanese, Korean, Chinese). To unlock them you must change the language in the
options menu, then play the game until the opening movie.

***** Thanks *****

To the writer of this guide, which was my main reference when writing this
walkthrough:
https://wiki.sunghwanyoo.com/game:%EB%B0%A9%EA%B5%AC%EC%84%9D%EC%97%90_%EC%9D%B8
%EC%96%B4_%EC%95%84%EA%B0%80%EC%94%A8

To the authors ot these two links, which provided additional information.
https://namu.wiki/w/%EB%B0%A9%EA%B5%AC%EC%84%9D%EC%97%90%20%EC%9D%B8%EC%96%B4%EC
%95%84%EA%B0%80%EC%94%A8
https://steamcommunity.com/app/869870/discussions/0/1841314700709791129/