Alrighty, so this is a guide to getting all of the endings :3 I've tried to make it as spoiler-free as possible!

Rue's Story 

This one is pretty straightforward :3 The choices mainly change the dialogue you get + depending on what you choose, you get different versions of certain scenes/see different things. None of the choices impact the main ending though aside from the final choice.

Choice 01:  
Go with her – Only changes dialogue  
Stay at home – Only changes dialogue

Choice 02:  
Approve – Only changes dialogue  
Disapprove – Only changes dialogue

Choice03:  
Invite her in – Continues the story without visiting Aku's house  
Let her leave – Causes Perry to become upset, leading to the same choice coming up again

Choice 04:  
Invite her in (2nd time) – Continues the story without visiting Aku's house  
Let her leave (2nd time) – Forces you down a path that leads to two endings If you picked 'Let her leave' twice, you will end up at Aku's house. Aku's house choice:   Kiss her back – Leads to ending 1 'Our Embrace (A)'   Shake her off – Leads to ending 2 'Our Embrace (B)'

If you invited Perry in, the story continues.

Choice 05:  
Tell her to move – Only changes dialogue  
Let her sit – Only changes dialogue

Choice 06:   
Kiss her – Changes dialogue and alters a later scene with Aku  
Slap her – Cuts the scene short + changes dialogue and alters a later scene with Aku + prevents you from getting ending 3 + locks you out of playing sexy scrabble with Perry later and some of the other choices

Choice 07: – If you picked 'Kiss her'  
Stop her – Cuts the scene short and changes dialogue + prevents you from getting ending 3 + locks you out of playing sexy scrabble with Perry later and some of the other choices  
Allow her to continue – Continues the scene and changes dialogue

Choice 08: – If you picked 'Kiss her' then 'Allow her to continue'  
Agree to let her stay – This leads to ending 3 'My Angel'  
Decline her offer – This continues the story

Choice 09:  
Hug her – Only changes dialogue  
Do nothing – Only changes dialogue

Choice 10: – If you chose to kiss Perry + allowed her to continue  
Tell her to back off – Cuts the scene short and changes dialogue  
Encourage her – Continues the scene

Choice 11: – If you chose to kiss Perry + allowed her to continue + encouraged her 
 Tease her – Takes you to the word puzzle – Pick 'Something else' then enter 'Checkmate or checkmate'  
Protest – Takes you to a potentially slightly NSFW scene with additional choices

Choice 12: – If you picked 'Protest'  
Do as commanded – Only changes dialogue  
Question her – Only changes dialogue

Choice 13:– If you picked 'Protest'  
How about no! - Cuts the steamy scene short  
Bring it! - Continues the steamy scene

Choice 14:  
Answer it – Leads to ending 4 'Oblivion' - This ending unlocks Perry's story and the extras section  
Don't answer it – Leads to ending 5 'Oblivious'

After viewing the 'Oblivion' end, you can access Perry's version of the story by clicking the image to the left of the main menu. However, because I am such a noob at Unity things, I couldn't get the buttons to work as intended. To actually get the button for that and the extras menu to work, you have to go into one of the other menus first (load, gallery, or settings) back out of that, then the button will be clickable. The extras menu is accessed by clicking on the red number 9. The load time is also very long when starting this route or going to extras. I need to add some additional load screens cos right now it just makes it look like the game is frozen >.<

Perry's Story

This one is a little more difficult to get a couple of the endings for, as this time around, when it switches back to Rue for the choices, there is a point counter going on in the background. This counter only impacts 1 set of endings – After Life A & B. For one, you will need to make sure that Perry's anger level is 4 or above. For the other, you will need to make sure that Perry's anger level is below 4.

Choice 01:  
Invite her in – Continues the story, avoids building up Perry's anger level  
Let her leave – Adds 1 to Perry's anger level

Choice 02:  
Invite her in (2nd time) – Continues the story  
Let her leave (2nd time) – Forces you down a path that leads to two endings If you picked 'Let her leave' twice, you will end up at Aku's house. Aku's house choice:   Kiss her back – Leads to ending 6 'Out In The Cold'   Shake her off – Leads to ending 7 'Our New Home'

If you invited Perry in, the story continues.

Choice 03:  
Tell her to move – Adds 1 to Perry's anger level  
Let her sit – Avoids building up Perry's anger level

Choice 04:  
Kiss her - Avoids adding to Perry's anger level + changes dialogue and keeps other options open later  
Slap her – Adds 1 to Perry's anger level + Cuts the scene short + changes dialogue + prevents you from getting ending 8 + locks you out of playing sexy scrabble with Perry later and some of the other choices

Choice 05: – If you picked 'Kiss her'  
Stop her – Adds 1 to Perry's anger level + Cuts the scene short and changes dialogue + prevents you from getting ending 8 + locks you out of playing sexy scrabble with Perry later and some of the other choices  
Allow her to continue – Avoids adding to Perry's anger level + Continues the scene and changes dialogue

Choice 06: – If you picked 'Kiss her' then 'Allow her to continue'    
Agree to let her stay – Leads to ending 8 'My Angel' (Perry's PoV version)  
Decline her offer – Continues the story

Choice 07:  
Hug her – Avoids building Perry's anger level + changes dialogue  
Do nothing – Adds 1 to Perry's anger level + changes dialogue

Choice 08: – If you chose to kiss Perry earlier on  
Tell her to back off – Adds 1 to Perry's anger level + Cuts the scene short and changes dialogue  
Encourage her – Avoids building Perry's anger level + Continues the scene and avoids Rue storming off

Choice 09:  
Tease her – Avoids the potential slightly NSFW scene  
Protest – Leads to the potential slightly NSFW scene

Choice 10: – If you chose 'Protest'  
Do as commanded – Only changes dialogue  
Question her – Only changes dialogue

Choice 11: – If you chose 'Protest'  
How about no! - Adds 1 to Perry's anger level + avoids the slightly NSFW scene  
Bring it! - Avoids adding to Perry's anger level + proceeds to the slightly NSFW scene

Choice 12:  
Kill Perry – Leads to ending 9 'Lingering Love' + opens up choices for more endings  
End it all – Leads to endings 10 & 11 depending on Perry's anger level
If Perry's anger level is 4 or above – Leads to ending 10 'After Life (A)' If Perry's anger level is below 4 – Leads to ending 11 'After Life (B)'

Choice 13: – If you picked 'Kill Perry'  
Kill Perry (2nd time) – Leads to ending 12 'All Fall Down'  
End it all (2nd time) – Leads to another choice

Choice 14: – If you picked 'End it all' (2nd time)  
Please leave – Leads to ending 13 'Letting Go (A)'  
Please stay – Leads to ending 14 'Letting Go (B)'

Aaaand that should be it! If you get stuck on anything else though or have any other questions, please don't hesitate to drop me a comment or an email and I'll do my best to help :3