Market Overview - The Nikkei share average closed down 0.14% at 50,842.93 after reaching a one-week high of 51,513.16 earlier in the day, which was a rise of 1.18% [1][6] - The broader Topix index gained 0.13% to finish at 3,321.58 [2][6] AI Sector Performance - Artificial intelligence-related shares were the primary drivers of the Nikkei's early gains, following a rally in Wall Street tech stocks amid optimism for an end to the U.S. government shutdown [2][6] - SoftBank Group, an AI-focused startup investor, initially surged by 5.55% before closing with a gain of 1.98% after announcing a 4-for-1 stock split and net profit that exceeded analyst expectations [5][6] Investor Sentiment - The afternoon trading session saw a decline in momentum, with the Nikkei index dropping as much as 0.65% at one point, as some traders opted to lock in profits [4][6] - Maki Sawada, a strategist at Nomura Securities, noted that there was "no single, big driving force" for stock gains, indicating a cautious sentiment among investors [4][6] Component Performance - On the day, 117 of the 225 components of the Nikkei index declined, while 105 rose and three remained flat [5][6] - Sony Group experienced a significant increase of 5.51% after reporting strong earnings during the midday trading recess [6] - Chip-making machinery manufacturer Tokyo Electron and chip-testing equipment maker Lasertec ended the day flat after shedding early gains, while Advantest saw a decline of 4.08% [6]