This is addtional content that enables the following songs:

Sweets Time
Gekokujoujou
USATEI 20XX
Solid
23145EASONS
Aunn by me
Aitsu ha Ikasama wo Shiteiru
SEE YOU AGAIN!
Chi no Iro ha Kiiro
Ayakashi set 14 Another ~Yoru ga Oritekuru
BURN IN HELL
Night's Dream (D.M.K. edit)
Hollow Masquerade
Hands(feat. AO, Rappubito)
Aestivalis(Danmakukagura Edit)
WARNING×WARNING×WARNING
Ford Stream
Kagerou-chan Tsuki ni Hoeru (Dankagu Edit)
Gensou Kappa Kousinkyoku(feat.ｙｔｒ)
Liminality
Konya, Syojo jya Irarenai
Atashimania
hareruya ga kikoeru
Unconscious Requiem（cosmobsp rmx）
Kachoufuugetsu
The Shining Law of the Strong Eating the Weak

More details on the official game page of Extra Song Pack 3 ...