That might be a reasonable basis for a rule in theory, but it's not the issue in this case under Japanese election law. Something that has any value and counts

That might be a reasonable basis for a rule in theory, but it's not the issue in this case under Japanese election law. Something that has any value and counts as a gift and therefore isn't allowed, even if the value is extremely small. There are other various other rules about campaign activity though (where/when it can be performed).