  In the deep narrow band image of the Coma Cluster taken with Suprime-Cam of
the Subaru telescope, we found an extremely long and narrow (~ 60 kpc x 2 kpc)
Halpha emitting region associated with a poststarburst galaxy (D100). Follow up
spectroscopy shows that the region has the same redshift as D100. The surface
brightness of the region is typically 25 mag(AB) arcsec^-2 in Halpha, which
corresponds to 0.5--4x10^-17 erg s^-1 cm^-2 arcsec^-2. We set two possible
explanations for the origin of the region; gas stripped off from a merged
dwarf, or gas stripped off from D100 by ram pressure. Either scenario has
difficulty to fully explain all the observed characteristics of the region.
