Maetropa has made this handy guide which explains how to reach the true end in the game! So I figured I'd post it here where it's easy for everyone to find :3
The first section is spoiler free, the section where spoilers begin is marked.
Make sure that you're playing this all on one save slot. For example, if your save is in Slot 1, you can't save and load from Slot 2 until you are on the ??? route. Once you get there, it's a bit counter intuitive,and you will want to make a backup save at the very beginning before the first choice in addition to the main save you overwrite as you play through. Don't touch the backup save until you've finished your first "complete" ending (you will know, because there will be a large pop up text with the name of the ending.
Inside your game folder is another folder called "bad end checklist"! As you are playing through a route, you want to keep track of how many bad ends you've reached. I'll write down how many endings per route there are, if you want to avoid spoilers, but the checklists have more specific titles if you're interested in that.
Unlike most other games, you WANT to get every single bad end (with exception to ??? which I will go into depth in the spoiler section). This is how you unlock the final ??? route. Don't worry about making backup saves this early, because upon choosing the choice that leads to a bad end, the game will then roll back and let you go with the correct option that leads to the best end.
There are several types of choices in the routes: death choices (which immediately lead to a bad end, fork choices, (which lead to a second set of choices which will either both lead to bad ends or one will lead to a bad end and the other return you to the good end path), flavour choices (this lets you explore different interactions!).
Once you get the good ending, you can replay the route again to find all the bad endings and cgs (with exception to ???, which is why you always want to keep an untouched save at the beginning.)
You can play the routes through in any order until you reach ???, but I recommend following the order they are listed in, since it feels like it's a nice drip feed of information on the broader story.
Student: 1 Good, 4 Bad
Mage: 1 Good, 7 Bad
Princess: 1 Good, 6 Bad
Detective: 1 Good, 7 Bad
Gamer: 1 Good, 8 Bad
???: 1 True, 2 Good, 14 Bad
You're not likely to have any trouble unlocking endings before the ??? route, since there are no hidden variables, and options have immediate consequences.
LOTS O SPOILERS
Now, in the ??? route, the rules change quite a bit, so I'll go into depth here. You can avoid all of the bad endings EXCEPT for the ones that I specifically say to take. Once you take them once and reach the bad end, it'll loop back and automatically choose the correct option, so don't worry about that.
To unlock the ??? route, you must view every single bad end in all the other routes.
**MAKE BACKUP SAVE 1 HERE**
Attack with the knife - Bad end 1
---> Run away
Defy - Bad end 2
---> Click the knife next to Kuro
I'm Fine - Bad end 4
---> My head hurts
Don't take his hand - Bad ending 4
---> Take his hand
No I don't - Bad end 4
---> I think so
Go on the attack - Bad end 3
---> Save the Girl OR Save the Boy
Who are you?
---> Have we met before?
Refuse to go with Kuro - Bad end 5
---> Go with Kuro
This is wrong - *NECESSARY* Bad end 6
---> They're wonderful
Shout at them - Bad end 7
---> Get between them
---> Follow the Sign
Stay - *NECESSARY* Bad end 8
---> Go back
---> Take the note
Refuse to take the note - Bad end 9
Kill her - *NECESSARY* Bad end 10
---> Resist the urge to kill her
[You can read them all here, they're all for flavour and don't advance the story or affect anything.]
---> I think that's enough for now
Try to talk him down - Bad end 11
---> Use Raine's gift
[You have to unlock all of the good endings of the other routes, otherwise you reach Bad ending 12.If you've viewed everything, this won't matter to you.]
---> Type Shiro
Type anything else - Bad end 13
**MAKE BACKUP SAVE HERE**
[At this point, you have viewed all three of the necessary bad ends.If you've viewed none of them, you automatically reach bad ending 14. If you view 1, or 2, the option for the true ending doesn't show up, so the ideal is to just view all of them by making a second backup here and reloading.]
This world is too cruel - Good end 1
This world is too damaged - Good end 2
---> This world still has hope left - TRUE end