In the North American and European versions, select the "Settings" option at the main menu, then "Enter Passwords". Enter one of the following case-sensitive passwords to unlock three copies of the corresponding card.
In the Japanese version, enter one of the following passwords, using katakana for syllables that are capitalized; hiragana for those in lower-case, and bracketed characters for those that are small.
gfghpba etmypmba
From the main menu, Settings > Enter Passwords
From the Main Menu, select Config and then Password. Enter the password shown to unlock 3 copies of the listed card. For rank, [N] = Normal, [R] = Rare, and [P] = Premium. For the password, hiragana is in lowercase and katakana is in UPPERCASE. Characters in brackets should be made small.
By earning Rhythmia, you can earn sets of the colored, Crystal Shards and thus unlock more characters. After a certain point, you will earn random Crystal Shards, or items if you have all the Shards you need - this starts at 9,750 Rhythmia and occurs every 1,000 ~ 1,500 thereafter.
By earning Rhythmia, you can obtain new sets of music, by game, for the Music Player.
By earning Rhythmia, you can obtain more Touch Sounds
Collect the indicated number of Rhythmia to unlock a Touch Sound.
By completing various tasks in the game, you will earn a Trophy - your whole collection can be found within the Records section of the Museum.
(Note that DLC content is not required for any of these; however, DLC can help to contribute to some, such as those Trophies accounting for this-many Summons and the like.)With the exception of the four characters you choose to start with at the beginning of the game, you will have to unlock the rest (so choose wisely). The majority of characters are unlocked by collecting Crystal Shards. There are twelve colors of Crystal Shards, and each character is aligned with a certain type. When you collect enough shards of one type, you can then choose (only) one character of that type to be unlocked. Then your Shards (of that type) will reset to zero. Unlockable characters that do not require collecting crystal shards are limited to Chaos (via Rhythmia) and the DLC packs' characters.