TOKYO—Japanese Prime Minister Fumio Kishida’s governing coalition kept a majority in a parliamentary election Sunday but was expected to lose some seats in a setback for his weeks-old government grappling with a coronavirus-battered economy and regional security challenges, according to preliminary results. Kishida’s Liberal Democratic Party (LDP) and its junior coalition partner Komeito together have won 274 seats as of late Sunday, with some 40 seats still undecided, in the 465-member lower house, the more powerful of Japan’s two-chamber Diet, public broadcaster NHK reported. The LDP has also won a single majority at 247 seats, with Komeito gaining 27 seats, according to NHK. Their combined strength has exceeded a parliamentary majority of 233 and also “an absolute majority” of 261 seats—a level that allows the ruling bloc to control all parliamentary committees and easily ram through legislations. But it also showed a loss from 305 seats previously. The LDP losses …