The first thing you should know is this achievement can only be obtained by completely watching all dialogues and all bad endings in the game. Therefore, the advice for you, BE SURE to save every time new dialogs appear. In the game, it is marked with a check mark if you have seen this dialogue, so that you do not get confused. You can check the missed dialogues in the main menu by selecting the Chapters option.
Missed dialogues will look like this "???". A little further down in the walkthrough, two dialogues will be described that you will 100% missed.

Start

When One Door Closes...
Starting the story


Collect my thoughts
Beat Goro at his own game
Sneak out, watch from a distance
Try and help it
Stay with Shimi
Check on the feral
A quiet meal
Try an ear rub
Ask her to give back the damn house keys!
Invite Veronika to eat with us
Do whatever it takes to save Shimi
Risk everything
Go after Shimi
Walk home

Where the Heart Is
Shimi's route

Start
Collect my thoughts
Beat Goro at his own game
Sneak out, watch from a distance
Leave it alone
Check on Pepper
Tease her
Stay with Pepper
Leave it alone
A quiet meal
Give the feral space
Ask her to give back the damn house keys!
Invite Veronika to eat with us
Leave the water on
Quickly feed Pepper, then i can focus on Shimi
Stay with Clawdia
Beat Pepper at her own game

Tipping the Scoville
Pepper's route

Start
Deal with this
Beat Goro at his own game
Sneak out, watch from a distance
Leave it alone
Go To Bed
Leave it alone
Something unexpected
Give the feral space
Ask her to give back the damn house keys!
Invite Veronika to eat with us
Go to Clawdia
I don't care what this guy thinks
Worth the risk
Stay with her on the sofa
Slow and steady wins the race
It's a little late for coff - Oh!
We'll live happily ever after!

The Cat's Meow
Clawdia's route

Chapters - Act 1 - Mama Mia

Start
Collect my thoughts
Beat Goro at his own game
Call the cops
Go To Bed
Leave it alone
A quiet meal
Give the feral space
She still wants to be with me, this is her way of reaching out.


Chapters - Pepper - Tempest in a Teapot

Start
Collect my thoughts
Beat Goro at his own game
Sneak out, watch from a distance
Leave it alone
Check on Pepper
Sit with her
Stay with Pepper
Leave it alone
A quiet meal
Give the feral space
Ask her to give back the damn house keys!
Invite Veronika to eat with us
Turn the water off
Pepper has to wait, take care of Shimi first.
Ask Veronika to help me with Clawdia


Now, after you have closed all the "???" in Chapters, you will receive the achievement:

Sic infit
One Hundred Percent