Apparently the Holiday's Least Boring Trend... from Japan!
Except it's called the Jimi festival (started in 2014) by a group of adults at Japanese lifestyle site Daily Portal Z. The idea is "we kind of wanted to participate in the festivities of Halloween, but were too embarrassed to go all out in witch or zombie costumes." Like "Someone who has spilled coffee all over himself" or "Shop attendant trying really hard to look away as you enter your PIN number." That'd be me!