Co-based shandites Co3M2S2 (M = Sn and/or In) are candidates of quasi-two-dimensional (Q2D) magnetism showing exotic properties. The interest is implied by its layered crystal structure that contains 2D-kagomé networks of magnetic Co atoms with antisymmetric Dzyaloshinskii-Moriya (DM) interaction and possibly spin frustration. The magnetism of Co-shandites have been previously investigated mainly using polycrystalline samples to show interesting magnetic properties. However, no experimental study from the above-mentioned viewpoint, Q2D kagomé system, has been carried out. For this purpose, investigations using single crystals are essential. In our study of Co-shandites, we successfully grew single crystals of two series-compounds of Co-based shandites, Co3Sn2-xInxS2 and Co3-yFeySn2S2, to investigate them as the Q2D kagomé system and we found novel properties using the grown single crystals, such as the highly Q2D itinerant electron magnetism and low-field anomalous phase very close to TC.