A topic from AEG's L5R CCG Rules forum, copied for Oracle of the Void from a copy of the forum saved in October 2015, so pages it didn't save are missing. Players' names are left out; the rules officials are named. Rulings are as they stood on these dates; later rulings, the rulebooks and the Rules Archive may differ.
Sachina Sensei
Interrupt, After the action shows cards in another player's hand, choose one of them. He may discard it; if he doesn't, he cannot play cards with that title this turn.
If Sachina Sensei is triggered and Show of Power (a card with the courage keyword) is revealed from my hand, should I choose to keep the Show of Power and not discard it am I correct in being able to later discard the card to pay for the courage player interrupt? Or does that count as the card being played?
Sachina Sensei
Interrupt, After the action shows cards in another player's hand, choose one of them. He may discard it; if he doesn't, he cannot play cards with that title this turn.
If Sachina Sensei is triggered and Show of Power (a card with the courage keyword) is revealed from my hand, should I choose to keep the Show of Power and not discard it am I correct in being able to later discard the card to pay for the courage player interrupt? Or does that count as the card being played?
You are correct. Discarding a Courage card for the Courage player ability is not "playing" it, so you CAN still do that in the scenario you describe.
From the CR, page 57, "Play: As a verb, “play” can refer to: putting into play a card type that normally enters play; using a Strategy card by putting it into the resolution area; bringing a Ring into play; or using an ability on a Ring that is out of play."