Cosmic rays (CRs) with energy up to the knee energy ( ~3 PeV) are believed to be accelerated by supernova remnants via the diffusive shock acceleration (DSA) process. However, based on the DSA model under typical supernova conditions, the maximum energy of CRs cannot reach to the knee energy. This is considered due to the weak interstellar magnetic field. Recently, direct numerical simulations of the DSA with magnetic field amplification by the Bell instability were performed by Inoue et al. (2021). They argued that CRs can be accelerated up to knee energy during the early phase of a supernova expansion in a dense circumstellar medium created by red supergiant wind. In this study, we focus on the propagation of gamma-rays produced by CRs in such a situation. The gamma-rays emitted at the shock front interact with soft photons from the supernova photosphere and cosmic background radiations. We calculate the evolution of the gamma-ray flux and estimate whether the CTA can detect such gamma-ray emissions. We found that CTA is able to detect 100 TeV gamma-rays from very young supernova remnants once per a few years.