  During 2020 April and May, SGR J1935+2154 emitted hundreds of short bursts
and became one of the most prolific transient magnetars. At the onset of the
active bursting period, a 130 s burst "forest," which included some bursts with
peculiar time profiles, were observed with the Fermi/Gamma-ray Burst Monitor
(GBM). In this Letter, we present the results of time-resolved spectral
analysis of this burst "forest" episode, which occurred on 2020 April 27. We
identify thermal spectral components prevalent during the entire 130 s episode;
high-energy maxima appear during the photon flux peaks, which are modulated by
the spin period of the source. Moreover, the evolution of the $\nu F_{\nu}$
spectral hardness (represented by $E_{\rm peak}$ or blackbody temperature)
within the lightcurve peaks is anti-correlated with the pulse phases
extrapolated from the pulsation observed within the persistent soft X-ray
emission of the source six hours later. Throughout the episode, the emitting
area of the high-energy (hotter) component is 1-2 orders of magnitude smaller
than that for the low-energy component. We interpret this with a geometrical
viewing angle scenario, inferring that the high-energy component likely
originates from a low-altitude hotspot located within closed toroidal magnetic
field lines.
