I'm even a little confused by your example: "me iré después que tú (I'll leave after you)." This phrase sounds like awkward Spanish to me, but admittedly I'm no expert.. The same with "Nos vemos después (see you later)," 'in which I would expect "luego" rather than "despues." Your example seems more like "I'll see you afterward" referring to a specific event rather than just "I'll see you later on." But I could be totally wrong about all of that. That's just the way it seems to me. Like I said, I'm no expert at all.