Soukyuu no Fafner

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.