We study the superdeformed (SD) states and corresponding SD hypernuclei of Ar isotopes with the multidimensionally constrained relativistic mean field (MDC-RMF) models, which can accommodate various shape degree of freedom. We found that the density profiles of SD states in Ar isotopes show a strong localization with a ring structure near the surface, while the central part of the density is dilute, showing a hole structure. This localization of SD density induces an appreciable deformation in the hyperon wave function and results in a large overlap between the core and the hyperon in the SD hypernuclei of Ar isotopes. Then the Λ separation energy of the SD state becomes larger than that of a normally deformed or spherical ground state. This feature is different from that found in other nuclei such as 32S, 56Ni, and 60Zn in which the Λ separation energy of larger deformed state is smaller. In this context, the measurement of the Λ separation energy may provide important information on the localization of the density profile of SD states.