質問: パスモを忘れてしまいましたけど、トイレに行くだけでもいいですか? does this sound natural? パスモを忘れてしまいましたけど、トイレに行くだけでもいいですか? does this sound natural?
回答: if you say it to station staff, you just say 駅内のトイレを使わせてくれませんか. you don't need to say anything more because the staff knows bathroom is only inside the gate. if you need ic card or the ticket, staff tells you about it and i think almost of the stations don't need the ic card to use the bathroom.