Mephistopheles wa Dare?Mephistopheles Who?; Who's Mephistopheles?; メフィストフェレスは誰？; 谁是梅菲斯特·菲雷斯

On the eve of the wedding Nanako Marina finds her fiance with another woman. Accidentally met her priest whispers: “Take revenge on him, lost sheep.“ What will happen to Nanako now, after a meeting with two-faced messenger of God?