(a) TESS light-curve (solid lines) and Hα equivalent width (open triangles) of YZ CMi around OISTER observation period. The left- and right-hand vertical axes indicate the relative flux in the TESS band and the equivalent width of the Hα emission line. The horizontal axes indicate the number of stellar rotation since BJD 2458498.329. (b) Same as panel (a) but for the light curve around APO observation period. (c) Rotational brightness modulations in the g (open squares), R_C (asterisks), and TESS (black dots; large flares were excluded) bands observed during the TESS cycle 7 and the rotational modulation of the Hα equivalent width (red triangles) obtained by OISTER observations; g-band, R_C-band, and Hα data indicate the average value during each observation run except for the data during flares. The rotation phase was calculated from equation (6). Blue dotted, orange dashed, and red dash–dotted lines indicate sinusoidal fits to g-band, R_C-band, and Hα line data. (d) Same as panel (c) but for the rotational modulations of the equivalent width of the Hα emission line obtained by APO observations. (Color online)