  We present photometric and spectroscopic observations of the Type Icn
supernova (SN) 2021ckj. Spectral modeling of SN 2021ckj reveals that its
composition is dominated by oxygen, carbon and iron group elements, and the
photospheric velocity at peak is ~10000 km/s. From the light curve (LC)
modeling applied to SNe 2021ckj, 2019hgp, and 2021csp, we find that the ejecta
and CSM properties of Type Icn SNe are diverse. SNe 2021ckj and 2021csp likely
have two ejecta components (an aspherical high-energy component and a spherical
standard-energy component) with a roughly spherical CSM, while SN 2019hgp can
be explained by a spherical ejecta-CSM interaction alone. The ejecta of SNe
2021ckj and 2021csp have larger energy per ejecta mass than the ejecta of SN
2019hgp. The density distribution of the CSM is similar in these three SNe, and
is comparable to those of Type Ibn SNe. This may imply that the mass-loss
mechanism is common between Type Icn (and also Type Ibn) SNe. The CSM masses of
SN 2021ckj and SN 2021csp are higher than that of SN 2019hgp, although all
these values are within the diversity seen in Type Ibn SNe. The early spectrum
of SN 2021ckj shows narrow emission lines from C II and C III, without a clear
absorption component, in contrast with that observed in SN 2021csp. The
similarity of the emission components of these lines implies that the emitting
regions of SNe 2021ckj and 2021csp have similar ionization states, and thus
suggests that they have similar properties of the ejecta and CSM, which is
inferred also from the LC modeling. Taking into account the difference in the
strength of the absorption features, this heterogeneity may be attributed to
viewing angle effects in otherwise common aspherical ejecta.
