For 3,000 JPY or so you can walk into a local Karaoke Box that offers No-mi-hou-dai or all-u-can-drink for various periods of time or the entire night. Most Karaoke boxes will offer this for shochu and draft beer but not for top shelf or call liquors.
They will bring you just as much beer or shochu as you can drink. The quality of alcohol that’s used in these joints is bottom of the barrel, so expect a serious hangover or futskayoi no-mi-hou-dai style.
This little drink called Ukon is to be consumed before drinking alcohol and it supposedly prevents a hangover. Made from mainly Ginger root it would make sense that this would work wonders for the stomach. I’ve tried Ukon myself and I’m not sure if it works or not. For 200 JPY I guess it’s worth a try.
