In this paper, we propose a novel microsensing scheme in which intrinsic sensing capability in microorganisms is utilized. Extraction of signals inside the cell and decoding of stimuli received would be an interesting challenge toward development of novel biomimetic sensors, or for potential utilization of a living microorganism itself as a microrobot. As a prototype, we focus on the mechanosensory process in Paramecium cells. When a mechanical stimuli is applied, Ca2+ ion concentration in the cell rises. By visualizing the Ca2+ level rise by using Ca2+ fluorescent indicators and input intensity data into PCs, we can extract the sensation perceived by the cell. A simple experiment was performed in vivo and contact sensation was successfully extracted and decoded. It can be applied for on-board sensors in cells as microrobots in future works.