In Go, the choice of black (first player) and white (second player) between players of even strength is traditionally done by chance. The method of selection is called nigiri (Jpn. 'grasping') . The older player takes a handful of white stones; the younger player then places either one or two black stones on the board, indicating a guess of odd or even. Next, the older player places on the board and counts the number of stones in his hand to determine whether there is an odd or even number. If the younger player has guessed correctly he will take black (first player); if not he will take white (second player).
I recommend using this method to assign the option to go first in L5R, using honor tokens for white stones and fate tokens for black stones. Honor tokens correspond well to the flavor of white stones (wisdom, strength) and fate tokens correspond well to the flavor of black stones (ambition, aggression). Disclaimer: Flavor in this case is not to be taken literally; Go stones may look tasty but they go down hard.
It would also be epic if FFG used Go proverbs as flavor text:
Check escape routes first.
There is death in the hane.
Make a fist before striking.
A rich man should not pick quarrels.
Give your opponent what he wants.
Do not go fishing while your house is on fire.
Fear is white's greatest ally.
I am Crane; heed my opinions.
Strange things are afoot a the Circle –K.
Wise man say, Forgiveness is divine but never pay full price for late pizza.
Wubba lubba dub dub!
Sources:
https://en.wikipedia.org/wiki/Rules_of_Go#Players
https://senseis.xmp.net/?GoProverbs
, if it wasn't obvious enough)