Japan is the only country among the world’s wealthiest democracies that has not legalized same-sex unions. Few celebrities are openly gay. Conservative groups oppose legislative efforts to protect the L.G.B.T.Q. community. But now, Netflix is introducing the country’s first same-sex dating reality series. Over 10 episodes of “The Boyfriend,” which will be available in 190 countries beginning on July 9, a group of nine men gather in a luxury beach house outside Tokyo. The format evokes Japan’s most popular romantic reality show, “Terrace House,” with its assembly of clean cut and exceedingly polite cast members, overseen by a panel of jovial commentators.