Atami lies at the start of the Izu Peninsula, and Shuzenji is further inland. Both locations are known for their Hot Springs and a great get away from Tokyo.

Atami is located approx. 50 minutes from Tokyo by the bullet, so can be made into a day tour. However, it is suggested that you stay overnight to get the real experience. 
A great get away for Japanese Couples also, Atami lets you walk the streets during the day, and then relax at a Onsen (Hot Springs) hotel at night. Located on the coastline, you can have views of Oshima Island in the distance.

The major attractions in Atami will be the Hot Springs themselves, although walking through the town lets you discover something new around each corner.  The Heiwa Dori Markets and arcades close to the station are still operational and is where the locals still purchase daily items. The MOA Art Museum brings people from all over the country to Atami and is an item that can not be left off your schedule. Izuzan Shrine is where the Red and White Dragons reside as does the God of Relationships. To make your relationship stronger, this Shrine is a great place to go, although be warn there are many stairs to climb. From the Shrine, you have beautiful views of Sagami Harbor.   
The waterfront area of Atami will let you take in the sea breeze, and the Atami Castle is high on the hillside.   Or you can see the  2000 year old Okusu Tree at the Konomiya Shrine, also noted as a powerspot.

Atami coast line is now registered as a Geo Site and the Nishigaura Coastline area is protected.  The share size of the cliffs and crashing water are impressive and also offer a panorama view of Atami City. 

Shuzenji is located further inland on the Izu Peninsula, and a location for people who want to get away from the hustle and bustle of “tourist oriented” destinations. A great alternate to Hakone and an atmosphere were you can relax amongst some incredible nature.  Shuzenji offers the luxury get away resort for people that are wanting the best possible hospitality. A local chicken is the delicacy here and used in seasonal dishes.  

Shuzenji sightseing is limited to the Shunzenji Temple, other Shrines and the Bamboo Forest. However, there are several nature walks that can be enjoyed and if you come in the right season, you can enjoy the Fall colors of the maple trees and Cherry Blossoms in the spring. The quaint town of Shuzenji is built along the Katsura River, and there are many Cafes, Bistros, ATMS and souvenir shops. 

To make the best of Shuzenji, it is recommended to stay two nights.  Upon arrival, you can see the sights of Shuzenji and then on the following day you can have a private car to take you to explore Izu Peninsula further. Traveling to the Fishing Town of Ito, will be a great introduction to Isu Peninsula’s very unique Geography. The coast line of Izu Peninsula is lined with sharp jagged rocks. Izu Peninsula was formed by underwater volcanoes that pushed an unique type of rock and magma to the surface and let to cool. The suspension bridge at Ito along with the Lighthouse offer a great chance to see this natural environment and maybe take a nature walk.