In this paper, we present the results from spectroscopic and photometric
observations of the M-type flare star YZ CMi in the framework of the Optical
and Infrared Synergetic Telescopes for Education and Research (OISTER)
collaborations during the Transiting Exoplanet Survey Satellite (TESS)
observation period. We detected 145 white-light flares from the TESS light
curve and 4 H$\alpha$ flares from the OISTER observations performed between
2019-01-16 and 2019-01-18. Among them, 3 H$\alpha$ flares were associated with
white-light flares. However, one of them did not show clear brightening in
continuum; during this flare, the H$\alpha$ line exhibited blue-asymmetry which
has lasted for $\sim 60$ min. The line of sight velocity of the blue-shifted
component is $-80$ - $-100$ km s$^{-1}$. This suggests that there can be upward
flows of chromospheric cool plasma even without detectable red/NIR continuum
brightening. By assuming that the blue-asymmetry in H$\alpha$ line was caused
by a prominence eruption on YZ CMi, we estimated the mass and kinetic energy of
the upward-moving material to be $10^{16}$ - $10^{18}$ g and $10^{29.5}$ -
$10^{31.5}$ erg, respectively. The estimated mass is comparable to expectations
from the empirical relation between the flare X-ray energy and mass of
upward-moving material for stellar flares and solar CMEs. In contrast, the
estimated kinetic energy for the non-white-light flare on YZ CMi is roughly $2$
orders of magnitude smaller than that expected from the relation between flare
X-ray energy and kinetic energy for solar CMEs. This could be understood by the
difference in the velocity between CMEs and prominence eruptions.