A super quick rec:
Five Ways They Might Otherwise Have Met by
redpocket Oshitari/Shishido, PG, 4542 words
Each snippet here is a different AU meeting between Oshitari & Shishido. This is exactly the sort of AU I like. Even though the ages & situations change in each snippet, it's still the same Oshitari & Shishido and the underlying dynamic between them is the same all the way through.
redpocket's done a lovely job of characterization and each AU is perfectly believable.