The COMET (Coherent Muon-to-Electron Transition) experiment is seeking to measure the neutrinoless, coherent transition of a muon to an electron in the field of an aluminum nucleus with a single event sensitivity below 10-16. The experiment utilizes a 8GeV proton beam provided at J-PARC (Japan Proton Accelerator Research Complex); and takes a staged approach to reach the final goal. The 1st stage of the experiment ( phase I ) uses 3.2kW proton beam, anticipated to start in 2016-2017 with a partial construction of the muon beam facility and a dedicated detector setup. The targeted sensitivity of the phase I is set below 10-14, which is about two orders of magnitudes better than the current limit (7 × 10-13) obtained in the SINDRUM II experiment at Paul Scherrer Institute in Switzerland. The 2nd stage ( phase II ) will follow this to reach the goal of the experiment with a complete facility setup and maximum beam power of 56kW. In this presentation status of the phase-I COMET and future prospects of the experiment including a possible upgrade plan using PRISM (Phase-Rotated Intense Slow Muon) as a muon source are explained.