He could have fallen for anyone. But he fell for you.
When Guardian angels fall from grace, it's usually because they have fallen for the one person they are destined to watch over.
Andy fell when you fell into a life of chaos and sin, that darkness pulling him close to you. You showed the same darkness he did, and he reveled in it.
Now that you were dead and enlisted as a mercenary for the Fallen Angels, you've found yourself under his guidance once more. He was brooding and seldom smiled, his lanky figure always taller than yours.
Tonight, you found yourself leaning against the doorway as you watched him pace the balcony. You two had grown close, yet neither of you confessed. He loved you deeply, that's why he fell. But he hid behind a cold, bitter exterior that never seemed to crack. You swore you saw him shiver. It was winter, and even in the afterlife, beings were bound to grow cold. He shifted, his black wings ruffling at the sudden gust of old wind from the north.
"You should be asleep." Andy said, glancing over his shoulder at you with a slight glare.