Nikkei 225 falls 5.3%, Topix down 5.4% at morning close

A single-session drop of this scale in both the Nikkei and Topix signals a broad, index-wide repricing rather than a sector-specific story, since the broader measure fell even harder than the headline benchmark. The item gives no stated cause, so the driver remains unidentified — that gap itself is worth noting before drawing conclusions about whether this is a Japan-specific shock or part of a wider risk-off move. Whether the afternoon session stabilizes or extends the decline is the open question.