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Quarterfinals of the 1st Beihai Cup: Tan Xiao faced Shin Jinseo. In their previous encounters, the two had only two recorded games, with Shin Jinseo maintaining a perfect win rate.
Black 31’s invasion was met by White 32’s attachment — a brilliant move that forced Black into overconcentrated shape. Locally, Black had no counterplay and had to seek opportunities in the upper-left. Black 35 onwards formed a standard ko sequence.
Shin Jinseo’s performance this game was uncharacteristically poor, with an unusually weak opening. When White 44 peeped , Black seemed reluctant to resolve the ko . Black 47’s knight’s move as a ko threat appeared careless. The upper-left ko’s resolution value rivaled the lower-left’s, and within just five moves, White secured a decisive advantage.
Diagram 1: Black 1 could have resolved the ko — White’s breakthrough in the lower-left was tolerable. Black 3’s diagonal move would preserve local flexibility, followed by Black 7’s extension to maintain pressure on White. For a player like Shin Jinseo, known for sharp endgame intuition , this sequence should have been straightforward. His choice to trade by capturing the corner might reflect fatigue from consecutive matches.
Diagram 2: Even as a ko threat, Black 47 should have been more aggressive. Black 1’s attachment is severe — if White tenukis as in the actual game, Black 3–5’s wedge and counter-hane would inflict greater damage on White’s territory, leaving White no room to escape. In the actual game, Black spent three moves merely securing the lower-left corner with low efficiency , gaining only marginal territory without pressuring White’s lower side.
The match concluded at Move 210, with Tan Xiao securing a middle-game victory.