Sunday Problem #31

Published 3 Jan 2021 by antti (last edited 10 Jan 2021)

This problem is from (Hiden Mondaishū, or Secret Problem Collection) by Hon dōjō, whose students include Fujisawa Rina 4p, Ichiriki Ryō 8p, and Shibano Toramaru 9p. The creators of the collection most likely had Igo Hatsuyō-Ron as their model, what with its originally having been a secret of the Inoue school, but having Mynavi openly publish the collection in spite of the title seems a bit strange.

Black to play.

Solution (1)
Black 1 and 3 are the correct order of moves. White 4 is the only hopeful resistance, turning this into a famous classic tsumego shape. Following, black 5 and 7 kill the white group.
Solution (2)
The best White can try is to resist with 8 and 10, but a bent four in the corner results – under Japanese rules, the white group is unconditionally dead.
Starting with this black 1 is wrong. Now, in response to 3, White can play 4, and his group forms two eyes.

Comments (2)

Tanukki wrote 5 months, 2 weeks ago:

Supposing that black can push at P17 and R16 and white blocks both, it becomes a J+1 group with a black first-line descent. Then black Q18, white R18, black S19 kills.

antti wrote 5 months, 1 week ago:

Solution added. Good job, Zdzieli!