East Gardens of the Imperial Palace (皇居東御苑) 皇居東御苑
It is the heart of Edo Castle; entry is free and it closes two days out of seven.
The eastern part of the imperial grounds, on the site of Edo Castle.
Tokyo
Takebashi, Otemachi, Jimbocho
Sword Art Online
Kirito and Asuna's date in the first episode of ‘Sword Art Online II’, the one that opens the Phantom Bullet arc: they meet in front of the Ōte-mon gate and walk in the park, and the three benches in a row on which they sit are on the open ground of the Honmaru, where the keep of Edo Castle stood. In the anime the scene is set in autumn.
All the places from Sword Art Online
https://theanimetrip.com/luoghi/giardini-orientali-del-palazzo-imperiale