Provided are a urethane prepolymer from which is obtained an adhesive which has excellent moisture permeability and which attains both low adhesion to skin and high adhesion to a base material, an adhesive, a skin patch material, an adhesive tape, a wearable device, and a wearable device kit. The present invention provides: a hydroxyl-group-terminated urethane prepolymer obtained by reacting an oxyalkylene polymer A having an average number of hydroxyl groups per molecule of 2.1 to 3, an oxyalkylene polymer B in which the number of hydroxyl groups per molecule is 1, and a diisocyanate compound, the number-average molecular weight of the oxyalkylene polymer B being 5000 or greater, and the content of ethylene oxide units in the hydroxyl-group-terminated urethane prepolymer being more than 10 mass%; an adhesive; a skin patch material; an adhesive tape; a wearable device; and a wearable device kit.
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