Yes. Japanese passport holders normally need an Ordinary Visa for tourism and can use Tanzania's online or visa-on-arrival facilities. Online preparation is the safer choice for a fixed safari or Zanzibar itinerary.
A Japanese passport does not provide visa-free entry for an ordinary Tanzania holiday. The usual category is the Ordinary Visa for a safari, Kilimanjaro trek, Zanzibar beach stay, family visit or other genuine tourism. The category follows the real purpose of the trip, not the name of a package sold by an airline or travel agency.
Japanese citizens are listed for both online and on-arrival facilities. That does not mean an arrival application is automatically faster or risk-free. Preparing online gives the traveller time to check the passport scan, separate portrait, first accommodation, return ticket and dates before boarding a long-haul flight. It also creates a record that can be tracked while the journey is still flexible.
One Tanzania visa can cover Mainland Tanzania and Zanzibar. The traveller should identify the true first international arrival in the form, then keep the rest of the route consistent. A grant notice permits presentation for entry; the final decision remains with Tanzania Immigration at the border.