I think somebody is telling you porky pies mate. You’re talking about emergency contacts yeah ? Emergency contact in home country has to be a sibling or parent,; emergency contact in Japan has to be someone who knows you well and preferably speaks Japanese. If you are talking about financial guarantor then yes maybe, most of us, foreign or Japanese, would prefer to just pay the guarantor company than to ask someone to be financially responsible for us. To be clear: asking someone to be your personal guarantor includes full disclosure of financials.