How do we unlock this in 1.5? I tried Googling, to no avail.

It's exactly like how Another Side, Another Story in KH was unlocked. 

get all keyholes, 99 Dalmatians, and torn pages as well as beaten the hades cup

Edited September 6, 201312 yr by Xamtweth-ReMIXed

Get the keyholes 99 Dalmatians and torn papers as well as the hades cup.

Final Mix Mode : Complete Hades Cup, Sealed All Keyholes (Including 100 acre Wood), Get all heartless into your Jimmy's memo (that means you've got to defeat Kurt Zisa and Phantom), Found all trinities, found all 99 Dalmatians, and complete the Jimmy's memo (every single detail of characters, and complete the mini games avaliable) 
 

Final Mix Proud : Sealed all Keyholes including 100 Acre Wood, and clear the Hades Cup

 

For more precisely.

 

Final Mix Mode : Complete Hades Cup, Sealed All Keyholes (Including 100 acre Wood), Get all heartless into your Jimmy's memo (that means you've got to defeat Kurt Zisa and Phantom), Found all trinities, found all 99 Dalmatians, and complete the Jimmy's memo (every single detail of characters, and complete the mini games avaliable) 

 

Final Mix Proud : Sealed all Keyholes including 100 Acre Wood, and clear the Hades Cup

 

For more precisely.

 

 You are correct  

Edited September 7, 201312 yr by CyborgHD13

Okay, I'm confused. (And I've been hearing different reports all over the Internet, which doesn't help). Can you unlock both "Another Side, Another Story" and "Deep Dive" in I.5?

 

And if so, and the above is how you unlock DD, then how do you get ASAS? I'm especially confused because in the original KHI, to get ASAS, you had had to seal all the worlds, complete the Hades cup, and find the dalmatians, but it seems that's how you unlock DD in Proud now?

 

Yeah, I'm definitely lost, so if anyone could help me, I'd greatly appreciate it. LOL.

What the others said , it's mostly the same with the original Kingdom Hearts .

You need also beat the secret bosses Phantom and Kurt Zisa not sure about Ice Titan, Sephiroth and MF. Probably.

All 101 dalmatians and all trinities. Just complete the journal.

Pretty much get everything in the game.

Okay, I'm confused. (And I've been hearing different reports all over the Internet, which doesn't help). Can you unlock both "Another Side, Another Story" and "Deep Dive" in I.5?

 

And if so, and the above is how you unlock DD, then how do you get ASAS? I'm especially confused because in the original KHI, to get ASAS, you had had to seal all the worlds, complete the Hades cup, and find the dalmatians, but it seems that's how you unlock DD in Proud now?

 

Yeah, I'm definitely lost, so if anyone could help me, I'd greatly appreciate it. LOL.

 

Another Side Another story was expanded to Another Side Another Story [Deep Dive] in KH1FM.  You don't have to unlock each individually you unlock ASAS and get the extra bit (Deep Dive) because it was added onto the end of it

 

Another side, Another story (KH1) criteria

 

Normal Difficulty

Beat the game with Complete Hades Cup; found all 99 Puppies; all Keyholes sealed

Expert Difficulty

Beat the game Sealing every Keyhole

 

****

 

Another Side, Another Story [deep dive] KH1FM criteria

 

Standard Mode

Beat the game with these conditions: Complete the Hades Cup; find all 99 Puppies; seal every Keyhole; complete Jiminy's Journal

Proud Mode

Beat the game after sealing every Keyhole and completing the Hades Cup.

 

You can apparently see them separately if you complete it first without clearing Jiminy's Journal to see ASAS alone, then do it again with the Journal complete (2 saves) and see ASAS Deep Dive, but I did it 100% in one run and saw them one after other.

 

Additionally what hasn't been mentioned is that you do have to defeat Unknown if you're on Normal as well to get the last Ansem Report (13) to complete Jiminy's Journal.  The information must have been copied from the original Japanese FM criteria where they were numbered 0-12 and people got confused in translating I guess.