66th Honinbo
# 66th Honinbo

The 66th Honinbo began league play on 7 October 2010 and completed on July 21, 2011. Title holder Yamashita Keigo retained his title over challenger Hane Naoki by a score of 4-3. Yamashita Keigo won the first three games, Hane Naoki the next three, and Yamashita Keigo the final game.

## Preliminary tournament

The preliminary tournament started on 8 April 2010. Hane Naoki, Iyama Yuta, Takao Shinji, and Cho U retained their place in the Honinbo league from the 65th Honinbo. These players were joined by the winners of the preliminary tournament: Cho Sonjin, Seto Taiki, O Rissei, and Kobayashi Satoru.

| Quarter-finals | Quarter-finals | Semi-finals | Semi-finals | | Final | Final |
| - | - | - | - | - | - | - |
| 13 May | 13 May | | | |
| Yamashiro Hiroshi | 1 | | | |
| Yamashiro Hiroshi | 1 | 17 June | 17 June | | |
| Fujita Akihiko | 0 | 17 June | 17 June | |
| Fujita Akihiko | 0 | Yamashiro Hiroshi | 1 | |
| 27 May | 27 May | | Yamashiro Hiroshi | 1 | |
| 27 May | 27 May | Takashima Takeshi | 0 | |
| Goto Shungo | 0 | Takashima Takeshi | 0 | |
| Goto Shungo | 0 | | | | 12 August | 12 August |
| Takashima Takeshi | 1 | | | | 12 August | 12 August |
| Takashima Takeshi | 1 | | | | Yamashiro Hiroshi | 0 |
| 20 May | 20 May | | | | | Yamashiro Hiroshi | 0 |
| 20 May | 20 May | | | | Cho Sonjin | 1 |
| Ohashi Hirofumi | 0 | | | | Cho Sonjin | 1 |
| Ohashi Hirofumi | 0 | 1 July | 1 July | | | |
| Uchida Shuhei | 1 | 1 July | 1 July | | | |
| Uchida Shuhei | 1 | Uchida Shuhei | 0 | | | |
| 27 May | 27 May | | Uchida Shuhei | 0 | | | |
| 27 May | 27 May | Cho Sonjin | 1 | |
| Cho Sonjin | 1 | Cho Sonjin | 1 | |
| Yamada Kimio | 0 | | | |
| Quarter-finals | Quarter-finals | Semi-finals | Semi-finals | | Final | Final |
| 13 May | 13 May | | | |
| Hoshino Masaki | 0 | | | |
| Hoshino Masaki | 0 | 10 June | 10 June | | |
| Kataoka Satoshi | 1 | 10 June | 10 June | |
| Kataoka Satoshi | 1 | Kataoka Satoshi | 1 | |
| 13 May | 13 May | | Kataoka Satoshi | 1 | |
| 13 May | 13 May | Obuchi Morito | 0 | |
| Obuchi Morito | 1 | Obuchi Morito | 0 | |
| Obuchi Morito | 1 | | | | 29 July | 29 July |
| Yasuda Yasutoshi | 0 | | | | 29 July | 29 July |
| Yasuda Yasutoshi | 0 | | | | Kataoka Satoshi | 0 |
| 13 May | 13 May | | | | | Kataoka Satoshi | 0 |
| 13 May | 13 May | | | | Seto Taiki | 1 |
| Yamada Noriyoshi | 0 | | | | Seto Taiki | 1 |
| Yamada Noriyoshi | 0 | 24 June | 24 June | | | |
| Akiyama Jiro | 1 | 24 June | 24 June | | | |
| Akiyama Jiro | 1 | Akiyama Jiro | 0 | | | |
| 27 May | 27 May | | Akiyama Jiro | 0 | | | |
| 27 May | 27 May | Seto Taiki | 1 | |
| Seto Taiki | 1 | Seto Taiki | 1 | |
| Mimura Tomoyasu | 0 | | | |
| Quarter-finals | Quarter-finals | Semi-finals | Semi-finals | | Final | Final |
| 13 May | 13 May | | | |
| Nakane Naoyuki | 0 | | | |
| Nakane Naoyuki | 0 | 24 June | 24 June | | |
| Nakano Hironari | 1 | 24 June | 24 June | |
| Nakano Hironari | 1 | Nakano Hironari | 0 | |
| 3 June | 3 June | | Nakano Hironari | 0 | |
| 3 June | 3 June | Kono Rin | 1 | |
| Ogata Masaki | 0 | Kono Rin | 1 | |
| Ogata Masaki | 0 | | | | 2 September | 2 September |
| Kono Rin | 1 | | | | 2 September | 2 September |
| Kono Rin | 1 | | | | Kono Rin | 0 |
| 20 May | 20 May | | | | | Kono Rin | 0 |
| 20 May | 20 May | | | | O Rissei | 1 |
| O Rissei | 1 | | | | O Rissei | 1 |
| O Rissei | 1 | 15 July | 15 July | | | |
| Mochizuki Kenichi | 0 | 15 July | 15 July | | | |
| Mochizuki Kenichi | 0 | O Rissei | 1 | | | |
| 27 May | 27 May | | O Rissei | 1 | | | |
| 27 May | 27 May | Yuki Satoshi | 0 | |
| Kamimura Haruo | 0 | Yuki Satoshi | 0 | |
| Yuki Satoshi | 1 | | | |
| Quarter-finals | Quarter-finals | Semi-finals | Semi-finals | | Final | Final |
| 22 April | 22 April | | | |
| O Meien | 0 | | | |
| O Meien | 0 | 10 June | 10 June | | |
| Kobayashi Satoru | 1 | 10 June | 10 June | |
| Kobayashi Satoru | 1 | Kobayashi Satoru | 1 | |
| 13 May | 13 May | | Kobayashi Satoru | 1 | |
| 13 May | 13 May | Ishida Atsushi | 0 | |
| Shida Tatsuya | 0 | Ishida Atsushi | 0 | |
| Shida Tatsuya | 0 | | | | 19 August | 19 August |
| Ishida Atsushi | 1 | | | | 19 August | 19 August |
| Ishida Atsushi | 1 | | | | Kobayashi Satoru | 1 |
| 3 June | 3 June | | | | | Kobayashi Satoru | 1 |
| 3 June | 3 June | | | | Suzuki Shinji | 0 |
| Mizokami Tomochika | 0 | | | | Suzuki Shinji | 0 |
| Mizokami Tomochika | 0 | 24 June | 24 June | | | |
| Suzuki Shinji | 1 | 24 June | 24 June | | | |
| Suzuki Shinji | 1 | Suzuki Shinji | 1 | | | |
| 13 May | 13 May | | Suzuki Shinji | 1 | | | |
| 13 May | 13 May | Cho Chikun | 0 | |
| Cho Chikun | 1 | Cho Chikun | 0 | |
| Takemiya Masaki | 0 | | | |

## League play

League play commenced on 7 October after the preliminaries, which finished on 2 September. Hane Naoki, who lost the Honinbo title to Yamashita Keigo the year prior, won the right to challenge Keigo for the title.

| Player | H.N. | I.Y. | T.S. | C.U. | O.R. | K.S. | C.S. | S.T. | Record | Notes |
| - | - | - | - | - | - | - | - | - | - | - |
| Hane Naoki | – | B+R | W+R | X | W+0.5 | B+R | W+R | B+R | 6–1 | Challenger |
| Iyama Yuta | X | – | B+R | X | X | W+R | B+R | W+R | 4–3 | |
| Takao Shinji | X | X | – | B+1.5 | X | X | W+R | X | 2–5 | Eliminated |
| Cho U | W+R | B+0.5 | X | – | B+3.5 | X | B+R | X | 4–3 | |
| O Rissei | X | W+R | B+R | X | – | X | X | B+R | 3–4 | Eliminated |
| Kobayashi Satoru | X | X | W+2.5 | B+4.5 | W+R | – | X | X | 3–4 | Eliminated |
| Cho Sonjin | X | X | X | X | B+R | W+11.5 | – | X | 2–5 | Eliminated |
| Seto Taiki | X | X | W+R | B+R | X | B+3.5 | W+R | – | 4–3 | |
