For application of a video camera of 1,000,000 fps, developed by the authors in 2001, to electron microscopes and biological microscopes, a next generation ultra-high-speed image sensor with photon-counting sensitivity is proposed. It is based on three key technologies, i.e., (1) ISIS, the In-situ Storage Image Sensor for ultra-high-speed continuous image capturing, invented by the authors, (2) CCM, the Charge Carrier Multiplication by impact ionization, invented by Hynecek, and (3) conventional back-side illuminated CCD. It works not only for ultra-high-speed and ultra-high-sensitive image capturing, but also for image capturing under illumination of ultra-violet, visible, and near-infrared lights, soft X-ray and electron beam. The sensor is named the PC-ISIS, the photon-counting ISIS. The concept of the PC-ISIS is presented. Difficulties in the realization of the PC-ISIS are discussed.