34th Single AKB48 Janken Tournament – My Take

I just finished watching the janken taikai clip after avoiding any spoiler for the last 5 days. It’s so much fun though I’d have loved an AKB girl to win it rather than Jurina (Personally, out of the senbatsu girls, I feel that Jurina is the one least needing of this center because she already co-fronts SKE and has centered a couple of singles, yet she actually won it…). Now I want to write something about it.

34th Janken Final


After avoiding stage48.net, my go-to forum for AKB news, it is kinda amazing to read that probably about 90% of the janken taikai threads is about whether it is rigged to make Jurina won or not. I still want to believe that it is all genuine. True she did win by throwing all papers, but here are a few points to show that perhaps, she had a good strategy and things just went her way throughout, without any help from high above.

  • Jurina ‘lucked out’ on a dominant strategy: 41% of all plays over the whole tournament is rocks (31% is paper and 27% is scissors), so throwing papers is actually a strategically dominant strategy.  Is this to do with Japanese traditional way of playing janken when they call ‘First is rock. Janken pyon’ (最初はぐう,じゃんけんぽん ), so a subconscious play to use is rock (something they say at the beginning)? I an interested to go through information from the other tournament to see if this trend holds
  • Her opponents played rocks throughout the tournament: Analyzing the patterns of each of opponents in all their rounds, it seems like they are all just very partial to playing rock even before they played Jurina. Their total share of rock play throughout the tournament is 62%, way higher than the tournament average of 41%.
Round Opponent Paper Rock Scissors
1 Muto Tomu 1 1 0
2 Yagura Fuuko 0 1 0
3 Shimada Haruka 1 4 0
4 Uno Mizuki 1 4 0
5 Tano Yuka 1 2 2
6 Hirata Rina 1 4 4
7 Kamieda Erika 2 8 2
Total Jurina’s opponent 7 24 8
Total Jurina’s opponents % 18% 62% 21%
Overall avg 79 104 69
Overall avg % 31% 41% 27%
  • Other players play one-hand strategies too: Other people also had similar strategies to Jurina. Kikuchi Ayaka threw 6 scissors in a row, getting her to the last 8. Takahashi Juri threw 7 rocks out of her 8 games. Okita Ayaka threw 4 rocks in a row. Jurina is not unique in her strategy, only in the fact that she won. Maybe Jurina saw Paruru’s scissors strategy last year and decided to follow it. If it is successful, why changed?

Other interesting fun facts about the tournament:

  • Best active tournament record: 83% (5-1) by Kamieda Erika, but she only has participated in one tournament. For those with more than one tournament, Matsui Jurina (8-2, 80%) won. With one loss from Uchida Mayumi (10-3, 77%), Shinoda Mariko now has the best all-time tournament record (10-2, 83%)
  • Best tournament record for NMB girls: Kamieda Erika (5-1, 83%). For those with
  • Best tournament record for SKE girls: Matsui Jurina, who else?
  • Longest match: 6 games between Kojima Maki vs. Iwata Karen (1st round) and Oba Mina vs. Kamieda Erika (games refer to a play between the two players resulting in either win/loss or a draw)
  • Most number of games: 12 by Oba Mina and Kamieda Erika
  • Watanabe Mayu continued her bad luck by once again losing in the last 32 round. What does it take her to win?
  • The luckless girls continued their streaks: Miyazaki Miho and Katayama Haruka lost in their first rounds again, making them the only members with 0-4 records. Sae and Shiori (the other 0-3 girls) did not participate
  • Maeda Ami crashed out in her first rounds.Would have loved to see her longer in the tournament. Really like her Vanellope dress! She still remains the only member with more than two janken senbatsu appearances though.
  • If you draw on the first game, throw a paper. Looking at the table below which show what a member threw in their second play after their 1st play is a draw, paper is the best play in most circumstances. If the first play was a rock, 63% of members played rock next. Similarly high rock share also occurred when paper was played (61%).  Thus, paper would have been the best strategy here. For a first play scissors, either paper or scissors would have been a statistically good play.
1st play Next play Code Count %
Rock Rock 1 24 63%
Rock Paper 2 7 18%
Rock Scisscors 3 7 18%
Paper Rock 4 14 61%
Paper Paper 5 6 26%
Paper Scisscors 6 3 13%
Scisscors Rock 7 3 17%
Scisscors Paper 8 10 56%
Scisscors Scisscors 9 5 28%

Final personal thoughts:

  • In the last 8, I was hoping that the two non-AKB (Jurina & Erika) would not win. Why did they both make it to the final?!?
  • With Jurina who has lost before winning this tournament, Eto Sayaka from HKT48 still remains the only undefeated member!
  • I am so sad that while NMB and SKE girls got to the final, none of the four HKT girls got into the senbatsus. Collectively, there is a 57% chance of having a HKT48 representative in this janken senbatsu. Shame that the coin toss came o
  • And finally. Sato Amina lost in her first game: ( I was so deflated. I really love her red riding hood costume too and wish she had more airtime with it. Is she left-handed? I didn’t even realize that. I also thought it was cute and so Amina the way she screamed when she lost. It sucks that her luck was non-existent again. In a way, it is fitting that her three senbatsu appearances are fan-pushed and she never got any help from lady luck or the management

Now I really want to go back to the play results in the earlier janken tournament to see whether the paper strategy would have worked as well in general.

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4 Comments on “34th Single AKB48 Janken Tournament – My Take”

  1. Thanks again for another informative post! Taking a look at the actual numbers helps to put things into perspective. Clearly, paper was the dominant opening in this tournament.

    There’s still validity to the claim that in order to rig the tournament, every girl must throw rock against Jurina, but rock is in fact the most common opener.

    Also, most people say that if no girl threw a different hand after watching Jurina win with paper every round, then it’s way too suspicious. Hindsight is 20/20.

    I don’t think any of the girls are serious enough where they map out their entire possible match tree and then determine what hands to throw against which girls. We all saw Jurina throw paper every match, but the girls inside the tournament probably weren’t as observant. I’m willing to bet there’s a very clear difference between watching the tournament and participating in it.

    I’ve done some research into competitive rock, paper, scissors and it’s quite fascinating. I wonder what the participants in those competitions think. Rigged or not? :P

    • Thank you so much for posting a comment:) Really glad to have a reaction on it and makes posting a blog worthwhile:)

      It’s just tough to draw any conclusion on rigging based on quantitative numbers. All it proves is that her strategy is a very viable one and if someone else less famous had won with it, no one would have made as big a fuss. I would be interested to go back and see all the matches Jurina played in, the reaction of the girls throwing their hands and how natural they are in their actions. If they were forced, I would have guessed something would look off in one of their actions. Jurina is also gave a much better reaction that Paruru, whose non-reaction made everything seemed that much more suspicious last year!

      Totally agree that it is easy for us to say the girl should have played scissors against Jurina. Even when I was watching this and typing the data on my excel, I didn’t even notice the all-paper strategy of Jurina. I mean, if I were playing this in the tournament, I would be more interested in just winning my game rather than looking towards the opponent in my next potential game!

      I am also really interested in hearing about your research on competitive rock-paper-scissors. Do let me know if you have written it somewhere in a blog:) If it gets that competitive, wouldn’t the best strategy always be to go as random as possible, keeping your chance at the even 1/3?

      One thing I am thinking about now is that human tends to think about conspiracy theory when the results look too neat. An analogy of this would be in a lottery (6 random numbers), if the winning number comes up to be 666 666, it would seem very odd and people would cry foul, whereas the number is as likely to come up as, say, 304 386 (which no one would think anything of). Jurina’s strategy just looks too neat for people to dismiss and with deep-rooted prejudice against AKB management, it makes it too easy to conclude it’s all a conspiracy…

      • Taka says:

        From what I have read on the subject the professionals are able to read their opponents or throw them off in some way in order to win the game. They usually play to 10 points and so people will try to control the pace of the game or induce some kind of predictable pattern in their opponent.

        Feeling the need to change your throw everytime is apparently a rookie mistake and easily exploited.

        http://www.nbcnews.com/id/44162400/

        http://www.slate.com/blogs/quora/2013/03/12/winning_strategies_for_rock_paper_scissors.html

      • Pretty cool articles. Thanks for sharing! I should remember it a bit more for any future game I’ll play. I always just wanted to be more random than the other player but it probably pays to out-think the other player. Interesting how the NBC News article backs up what all the AKB ‘rookies’ were doing, namely, throwing more rocks than usual. I guess just like the second article says, it is a lot tougher to strategize in a one-and-done game.

        On the truly random topic, my brother read a book about rock-paper-scissors and he told me that a plan to make things truly random is to remember pi and base all you move on the sequence(3.141592…, when 1-3 is rock, 4-6 is scissors, 7-9 is stone, 0 is skip to next number).


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