Shares of Japan's SoftBank Group plunged, following a broader slump in AI-related stocks as investors once again grew wary of the sector's lofty valuations.

The AI-led rally has pushed the S&P 500's forward P/E above 23—its highest since 2000, according to FactSet.

Shares of major tech companies have fallen in the US and Japan over fears about the valuations of firms linked to AI.

Shares of Japan's SoftBank Group plunged, following a broader slump in AI-related stocks as investors once again grew wary of the sector's lofty valuations.