Once something is dubbed cool, it is often just a matter of time before it ceases to be so. Ranked No. 8 on Time Out’s “world’s coolest neighborhoods” list, Nakatsu in Osaka has gained international attention — but locals worry its distinctive character faces a greater threat than fleeting fame. Home to a population of little more than 10,000 and crammed between two train lines and the Yodo River, you’d be forgiven for never having heard of or been to Nakatsu.