The μ-SKY Limited Express, the Rapid Limited Express and the Limited Express trains have First class cars which require a railway ticket and a First class car ticket. (The ticket costs 360 yen and is called a "μTicket".)
Seat reservations are made when you purchase a μTicket. If you board a First class car without a μTicket, please pay the surcharge to the train attendant. In such cases, seat reservations cannot be made.