It hurts me to not see a romance tag on this because I want to see these adorable feelings flourish. Jade's clearly already hooked so we just need our main character to properly fall for him! I don't know if the tag isn't there because nobody's added it or if it isn't there because in the source material nothing happens, but I really hope it's the former; they're so cute together! Plus it would add another interesting twist to things if they have to deal with that whole issue of what happens when the sisters go back. He doesn't really have much going for him here without her so they should kidnap him to Japan when the time comes if they still want to go.
Also, re: beer
If they have wheat they should have beer, it dates back past 10,000BC. Pretty much since we've had agriculture we've had booze because that's people for you. Actually, not even wheat. Any cereal grain. All over the world as soon as people started having it at their disposal they immediately began turning it into alcohol.