The plenary session of Thursday afternoon will end earlier than the other days. You may be able to organize an excursion on your own. The conference venue is in the center of Nagasaki city, and is easily accessible to many tourist attractions. Here are some places to visit that are close to the venue (within 3km). You can find more information from
Discover Nagasaki - the offficial visitors' guide -
https://www.discover-nagasaki.com/en/featured-topics/about_nagasakicity
Japan-guide.com
https://www.japan-guide.com/e/e2162.html
Nagasaki Peace Park and Hypocenter Park (commemorating the atomic bombing)
Nagasaki Atomic Bomb Museum (open from 8:30 to 17:30)
https://nabmuseum.jp/genbaku/
(choose your language from the tabs in the upper-right corner)
Twenty Six Martyrs Monument
(Dedicated to 26 Christians who were executed in 1597)
https://www.japan-guide.com/e/e4417.html
Dejima
(Former district reserved for Dutch traders, open from 8:00 to 21:00)
https://nagasakidejima.jp/english/
Chinatown: Tojin-yashiki (former Chinese settlement)
https://www.japan-guide.com/e/e4404.html
Glover Garden
(including the oldest wooden Western-style building in which a Scottish merchant Thomas Glover (1838-1911) lived, open from 8:00 to 21:30)
https://glover-garden.jp/
(choose your language from the tabs in the upper-right corner)
Oura Church
(the oldest Catholic church, designated as a national treasure and one of the constituents of the world heritage, open from 8:30 to 18:00)
https://www.japan-guide.com/e/e4407.html
https://www.discover-nagasaki.com/en/sightseeing/102
＊Map from https://www.japan-guide.com/e/e4410.html
