Credits option:
Complete One More Extra Stage; every Nonstop course; or the Paranoia Brothers 
Oni course. 

Dancer options:
Play any course in Nonstop mode. 

Endless mode:
Get 100 "A" or greater ranks (except in beginner mode) 

2MB (Dancer):
Play MAX.(period) with player one. 

A Stupid Barber:
Complete the Funky Groove Nonstop course. Alternately, successfully complete 
Lesson mode. 

Burnin' The Floor (Momo Mix):
Complete the Naoki Neo-Standard Nonstop course. 

Dance Dance Revolution:
Play every song, then play about another twenty songs. You will then see it on 
your song list.

Emi (2) (4th) (dancer):
Complete fifteen songs with Emi (1) (4th) as a dancer. 

Keep On Liftin':
Pass every Nonstop course 

MAX. (period):
Pass MAX. (period) as your EXTRA STAGE 

MAX.(period):
Play every song. Alternately, complete Legendary Road Oni course. You will then 
see it an Extra Stage.

More deep (ver. 2.1):
Intentionally fail an Oni course. 

Naoki Premium:
Complete the Naoki Neo-Standard Nonstop course. 

PARANOIA Survivor Max:
Get an "AA" or greater rank in all songs in the Paranoia Brothers course under 
Heavy mode. 

Paranoia Survivor MAX:
Get an "AA" rank on every song in the Paranoia Bros. Max 2 Oni course. Note: 
Sometimes you might see it on your song list, but you cannot play it on challenge. 
You will only see it a few times.

Paranoia Survivor:
Complete Paranoia Brothers Oni course. Alternately, complete any of the songs in 
the course under Heavy mode. 

The Legend Of MAX:
Pass The Legend Of MAX as your extra stage. 

The Legend Of MAX:
Play every song. Alternately, successfully complete the Extra stage. 

Tomorrow Perfume:
Get an "AA" rank or greater. 

Trip Machine survivor:
Get an "A" or better rank on Trip Machine Survivor under Heavy mode as as semi-
final stage. 

Try 2 Luv. U:
Get twenty "A" or greater ranks (except in beginner mode). Alternately, complete 
Lesson mode. 

U1 (dancer):
Play MAX. (period) as player two. 

Un Deux Trois:
Get fifty "A" or greater ranks (except in beginner mode). 

Xenon:
Get an "A" or greater rank on V (for Extreme) challenge. 

Additional Dancers option:
Complete every Nonstop course 

Angel's Oni course:
Complete ten Oni courses 

Brand New Songs Oni course:
Complete the Brand New Songs Nonstop course. 

Brand New Songs Nonstop course:
Complete A Stupid Barber. 

Darkness Oni course:
Complete any song with the "dark" setting. 

From GF & DM Oni course:
Receive an "A" or better on Mikenko Rock in Heavy mode. 

From IIDX Oni course:
Complete one Oni course. 

IIDX Boss Oni course:
Complete V (for EXTREME) challenge with an "A" or greater rank. 

Legend Road Oni course:
Pass True Demon Road Oni course 

Legendary Road Oni Course:
Play every Max song. Max songs do not have to be beaten; just played.

Max Quartet Nonstop course:
Pass MAX. (period) as your EXTRA STAGE 

Rap 5 Oni course:
Get an "A" or greater rank on Daikenkai challenge. 

Rebellion of Oni (Oni course):
Master Light, Standard, or Heavy mode. 

Remix Nonstop course:
Complete the Standard Nonstop course. 

RevenG and TaQ Oni course:
Complete five Oni courses. 

Reverse Oni course:
Complete any song in Reverse mode. 

Road of 2MB Oni course:
Complete MAX. (period) as your extra stage. 

Slow Road of Oni (Oni course):
Get an "A" or greater rank in bag heavy mode. 

True Demon Road Oni course:
Complete 20 Oni courses. 

Ultra 16 Oni course:
Complete the Legend Road Oni course.