"I think they're having an affair," murmurs my companion, the ever-observant Megumi. She nods at a middle-aged couple sitting next to us on the "Romance Car," the limited express train that links Tokyo and the hot-spring resort of Hakone, Kanagawa Prefecture.
"How can you tell?" I ask.
"They're too flirtatious. At their age, married couples don't have that much fun."