The species produces small mushrooms with white caps and very short, very thin black stems.

Found in June, the species grows on dead Sasa leaves, from which it takes its specific epithet.

Marasmius sasicola was first described by Haruki Takahashi (2002) in an article in Mycoscience, based on specimens collected from Ikuta Ryokuchi Park, Kawasaki, Kanagawa Prefecture, Japan in 2000 and 2001.

Within the genus Mycena, it probably belongs to the section Marasmius, and the subsection Penicillati, due to characters of the stem, gills and pileipellis (the outer-most layer of the cap).

[2] Marasmius sasicola produces mushrooms that have convex caps from 5 to 10 millimetres (0.2 to 0.4 in) in diameter featuring folds or striations.

The pileipellis, the top layer of the cap, forms a hymeniderm, a cell structure reminiscent of the hymenium on the gills.

The stipitipellis, the outermost layer of the stem, is made up of cylindrical hyphae measuring from 3 to 6 μm in width, which run parallel to one another.

The smooth cell walls are colorless, but again stain a dark reddish-brown in Melzer's reagent or Lugol's solution.