That's implied. If you're working with your tourist visa you're changing the purpose of your stay and thus lying regarding your visa declaration:
> Single-entry short-term stay visa for the purpose of Tourism (for a period of up to 90 days) (Note).
> [...]
> If you wish to visit Japan for other purposes or for a long-term stay, please submit your application to the Japanese Embassy, Consulate General or Consular office with jurisdiction over your place of residence.