The setting is modern-day Japan, somewhere in Tokyo (the exact city isn't specified).
The question: would a male officer be allowed to wear a wedding ring? (He's just a regular officer who works at a koban, not a sergeant or of high rank.) If so, are there any restrictions on the ring -- does it have to be a plain band, or can there be a stone on it?
eta: The ring does canonically have a stone. I can't get around this bit, sorry. :)