I rode this nice series E261 train last year with my family. This is really our nice memory.
One special thing is that deluxe compartment rooms (“green car” status) are provided.
From the compartment, we enjoyed nice view of sea from Izu Peninsula, and viewed Izu seven Islands because of nice weather!
They also have a bar car but its service was suspended at that time due to the pandemic, unfortunately.
Shimoda, the terminal of Izukyu Railways, is an interesting town to visit. It is about 3 hours from Tokyo by train. Having a port, it has an important place of Japan – US relations in 19th century.