Korean and Japanese automakers have taken strikingly different paths into the electric age. Hyundai Motor Group moved early into battery electric vehicles (BEVs), while Toyota and its peers—path- dependently committed to hybrids—rationally delayed. We ask whether this divergence produced a measurable gap in carbon emission intensity (CEI), whether the gap is reflected in firm value, and whether the EU Emissions Trading System (ETS) carbon price sharpens the link between the two. Using a panel of three Korean and eight Japanese listed automakers over 2019–2024 (66 firm-year observations), we estimate an event-study difference-in-differences specification for the CEI gap and two-way fixed-effects regressions for firm value. The Korea–Japan CEI gap widens sharply in 2021, the year of IONIQ 5 production (δ_2021 = −5.30, p = 0.010), and fades by 2024 as Japanese OEMs launch their own BEVs—the delay-then-follow profile that path dependence predicts. The short-run gap operates through the revenue-composition channel rather than plant-level emission cuts. The ETS × CEI interaction is flat for Tobin’s Q but significantly negative for ROA (β = −0.0000376, p = 0.003), though this result is sensitive to the CEI measure and should be read as suggestive. Carbon risk thus appears to hit realized earnings before it is written into market valuations.