Bonus when you beat the game
     After  you  beat  the game you get the option Omake added to your
main  menu.  It  has the options: Album (view scenes from the game you
have  already  seen), BGM player, and Free Play (lets you retry any of
the  missions in the game). Look carefully at the Free Play menu list,
because  after the main list of 12 missions, there are some b missions
shown, which are any side missions you unlocked.