Ch. 1: Unexpected letter?

A year passed since a red haired reaper and a stern reaper broken up. Nothing caught the red reaper's love interest besides an open invitation coming from a foreign school across the seas.
Who would send this, and what is the mysterious being's purpose?

((This is my first fanfic! It'll be lengthy, please bare with me ^^;; But more importantly, I hope you enjoy it!))