Upon Silver Wings (Sekirei x Angel Reader)

I Haven't seen many of these around, so I thought I'd have a try:

Even amongst the angels, F/N was old. Though he wore the skin of a young man, he had seen the last of the God-wars, and since their conclusion the eight seraphim had sealed much of his power.
However, this may be about to change. When his master, the seraph Azrael instructs F/N to go to Japan, and investigate what has become of the S-plan set up by F/N's late friend Takehito Asama. Doing so could regain his power, and stop a new God-war.