インターネットオフライン時の帰属表示は必要？

You could cache the tile attribution information similarly to the tiles. That said, you could manually capture the main attribution information and just show all of them. The main ones are:

• Zenrin - Show this if you are showing road maps of Japan.
• TomTom - Show this whenever showing road maps outside of Japan.
• Vexcel - for satellite imagery zoom levels 13 or more.
• EarthStar Geographics - When showing satellite tiles between zoom levels 0 and 12.
• OpenStreetMaps - It's used in some places with the road map data. I think mainly for building footprints. You could also just use "OSM".

To simplify things:

• For satellite imagery with road data I would show "© 2024 TomTom, OSM, EarthStar Geographics, Vexcel "
• For satellite imagery, that has no road data I would show: "© 2024 TEarthStar Geographics, Vexcel"
• For all other maps you will likely be best to show something like "© 2024 TTomTom, OSM"

If you are showing maps of Japan, replace TomTom with Zenrin. For good measure you could have the year set programmatically to the current year to keep things looking current.

All that said, when it comes to map tiles, the product terms say the following about caching: "Results may not be stored for longer than: (i) the validity period indicated in returned headers; or (ii) 6 months, whichever is the shorter." Taking a quick look at a network trace when using Azure Maps, it looks like the cache header is 1 year, so point (ii) would apply, which means you could cache map tiles for up to 6 month.

Be sure to review the Azure Maps Product terms: https://www.microsoft.com/licensing/terms/welcome/welcomepage