I would really be pissed if Sakurako is RUM, whether it makes sense or not, I just don't like the idea. As a matter of fact, to me at least, it's highly unlikely for her to be RUM, she's too young, 23, and that is really her true age since 2 other characters know her form childhood, and I think RUM, the second in command in the Black Organization, should be old, I just don't see the boss trusting a new member younger than most other members with the second in command rank.