Oil Shock and Korean Semiconductor Rout Hammer Nikkei 225; Banks and Select Defensives Buck the Trend

Japan's benchmark index dropped 1.92% as geopolitical risks and a semiconductor sell-off outweighed gains in banking stocks on rate hike expectations.

A toxic cocktail of escalating US-Iran hostilities and a brutal sell-off in South Korean chip stocks sent the Nikkei 225 careening lower on Monday, snapping a three-day winning streak. Japan’s benchmark index plunged 1,315.00 points, or 1.92%, to close at 67,242.73, after touching an intraday low of 66,653.11 before bargain hunters pared some of the losses. The day’s decline wiped out a large chunk of the previous week’s tech-driven gains and marked the index’s worst session in months.

The geopolitical flashpoint came over the weekend when the US Central Command launched retaliatory strikes against Iranian targets following an attack on the merchant vessel MV GFS Galaxy. Tehran retaliated with threats to blockade the Strait of Hormuz and struck targets in the United Arab Emirates, Qatar, Kuwait, Oman, and Bahrain. Washington denied the strait was actually closed, but the mere prospect of disruption sent Brent crude surging past $79 a barrel — the highest since late June — and rattled energy-sensitive Asian markets. For Japan, a major energy importer, the oil spike compounded existing worries about input costs and supply chains.

Yet the most immediate damage to the Nikkei came not from oil but from across the Sea of Japan. South Korea’s KOSPI crashed more than 8% at one point, triggering a trading halt, after SK Hynix — fresh off its Nasdaq debut on July 10 — plunged as much as 15% in Seoul, while Samsung Electronics shed roughly 10.7%. That semiconductor rout quickly infected Tokyo: chip-equipment maker Advantest alone subtracted 243.77 points from the Nikkei, and together with Kioxia Holdings it accounted for about 272 points of the decline. Kioxia tumbled 9.3% to 69,850 yen, weighed further by a Bernstein sell rating and a 40,000-yen price target, with the analysts pointing to upcoming earnings from ASML and TSMC as key catalysts for the memory sector. Tokyo Electron also featured among the losers.

The damage was broad but not universal. Yaskawa Electric led the percentage decliners with a 14.34% collapse, followed by Taiyo Yuden at 12.86%. Fast Retelling slid 2.1% as investors rotated out of consumer names. The wider TOPIX index fell a more modest 0.2% to 4,027.82, underscoring the selective nature of the sell-off. Twenty-one of the 33 Tokyo sectors closed in the red, and trading volume surged well above the 30-day average, reflecting acute nervousness.

Defensive and cyclical pockets provided a stark counterpoint. Banking stocks stood out as the day’s strongest pillar: Mitsubishi UFJ Financial Group gained 2.4%, Sumitomo Mitsui Financial added 2.1%, and the sector was buoyed by persistent expectations of further Bank of Japan rate hikes. Mitsubishi UFJ even overtook both Toyota and Kioxia in market capitalisation during the session, reaching $258.6 billion — the first time a Japanese bank has claimed the top spot since Sumitomo Bank did so in 1986. The re-rating reflects a broader capital rotation from overheated AI and tech names into financials. Other winners included SUMCO Corp, which rallied 7.9% on sector-specific demand, and SoftBank Group, which rose 2.0% thanks to its diversified global portfolio. Ryohin Keikaku, operator of Muji stores, was also among the positive contributors.

The yen remained under pressure, trading around the 162 mark against the dollar amid a flight to the US currency driven by the Gulf crisis, though it briefly strengthened to 161.70 earlier. For Japanese exporters, that offers a mixed bag: a weaker yen supports overseas earnings but raises import costs, especially for energy. The Brent oil spike above $79 is a clear headwind for the entire industrial base.

Technically, the Nikkei ended the day above several key support levels, but the damage was clear. The index pierced the psychologically important 68,000 mark and now sits just 1.57% above its 50-day moving average of 66,201.69 points, while the 200-day average at 56,066.43 remains a distant 19.93% lower, confirming the long-term uptrend is intact. On a 12-month basis the benchmark is still up 70.41%, and year-to-date gains stand at 31.45%. However, the RSI dropped to 47.4, sliding from overbought territory, and the annualised 30-day volatility of 35.94% signals elevated anxiety. The index is now 7.67% below its record high of 72,831.73 reached on June 22.

Traders are watching the 66,800 zone as a potential floor for the current correction; a break below that could open the door to the 65,000–65,800 range. For now, the Nikkei futures on the Chicago exchange, at 69,250 — roughly 440 points above the Osaka close — hint at a possible stabilisation. All eyes now turn to US inflation data, the start of earnings season from major American banks and chip bellwethers TSMC and ASML, and of course the next twist in the Middle East crisis. Whether the geopolitical risk premium in oil holds or fades will likely dictate the direction for Japan’s market in the sessions ahead.