Fate/Grand Order Lostbelt No. 3: SIN

Shortly after Chaldea settles in at their new base, an assassin strikes, attempting to poison members of their group. In a desperate bid to save the lives of the assassin's would-be victims, Chaldea makes its way to the third Lostbelt, hoping to find an antidote.

They arrive in a land of eternal peace, brought on by the end of all conflict between nations. This land knows no struggle, no tragedy, no fragility...a truly idyllic world. Time passes gently, and the people live comfortable lives. And yet...