Hydrogenated block copolymer and composition containing same

To provide a thermoplastic elastomer composition excellent in fluidity, compression set property, and flexibility, and a hydrogenated block copolymer that provides the composition. The hydrogenated block copolymer is obtained by hydrogenating a block copolymer which is obtained by reacting a living polymer represented by the following formula (1): B1-A-B2-X (1) wherein B1 and B2 each represent a polymer block mainly including a structural unit derived from a conjugated diene compound, A represents a polymer block mainly including a structural unit derived from a vinyl aromatic compound, and X represents an active terminal end of a living anion polymer, with a coupling agent, wherein the ratio of the mass of the polymer block B1 to the total mass of B1 and B2 before hydrogenation is from 0.10 to 0.45; and the content of the structural unit derived from the vinyl aromatic compound is from 25 to 50 mass % based on the mass of the hydrogenated block copolymer.