Here is the full list of all 24 BBirthday - there are Visual Novel achievements.
Complete EP15D
Defeat Mr. Rose on Hard Mode
Complete EP14N
Defeat Jovana and Giovana on Hard Mode
Defeat Win Nightmare on Hard Mode
Complete EP13N
Defeat Alice Nightmare on Hard Mode
Complete EP 12N
Complete EP 11ND
Defeat Mary and Magdalene on Hard Mode
Complete EP1-10N
Complete EP15N [Love]
Complete EP15N [Coffee]
Defeat Mr. Love on Hard Mode
Defeat Miss Coffee on Hard Mode
Get ending 23
Get ending 24
Get ending 25
Get ending 26
See the credits scene
Unlock all endings of the main story
Complete the costume minigame with a perfect score
Find the 3 VT Harmony plushies hidden on first maze of EP11ND
Complete maze of EP Final[C] in one try