Inspection of the g-band excess. Left: XS spectrum obtained at t − t₀ = 1.5 day (observer-frame). A SPL (red line) was fit to the spectrum in the wavelength range 6000 ≤ λ ≤ 9000 Å (3 − 5 × 10¹⁴ Hz). Between 3000 ~ 5500 Å (5.5 − 8 × 10¹⁴ Hz), excess above the best-fitting SPL is seen. Over-plotted is the g-band transmission curve, which shows that the excess occurs only in this filter. Right: optical & UV SED evolution (AG+SN+host), using data taken from our ground-based telescopes and Swift-UVOT. The g-band photometry are shown as stars. At early times (t − t₀ = 0.95 day), little excess is seen in the g-band. However, between t − t₀ = 2.56 − 6.12 days, a clear excess is seen, which disappears by 7.64 days. Intriguingly, excess is not seen in the bluer UVOT filters.