Enzymatic biofuel cells have attracted much attention for their potential to directly use biochemical energy sources in living organisms such as animals, fruits, etc. However, generally natural organisms have a skin, and the oxygen concentration in the organisms is lower than that of biofuels like sugars. Here, we fabricated a miniature assembly that consists of a needle bioanode for accessing biofuels in organisms through their skins and a gas-diffusion biocathode for utilizing abundant oxygen in air, for the first time. The performance of the biocathode was fourfold improved by optimizing its hydrophobicity. The assembled device with a needle anode for fructose oxidation was inserted into a raw grape, producing a maximum power of 26.5 μW (115 μW cm-2) at 0.34 V. A light-emitting diode (LED) with the cell served as a self-powered indicator of the sugar level in the grape. Power generation from blood sugar was also investigated by inserting a needle anode for glucose oxidation into a blood vessel in a rabbit ear. Prior coating of the tip of the needle anode with an antibiofouling agent was effective to stabilize output power.