One of the best shio ramen shops in Japan is out in Atsugi. Honmarutei is a shop so good that I couldn't really recommend anything else in the area. But, if they are closed, Menyashokudo is a nearby choice.
The shop is done up in 昭和レトロ style; Showa retro. Old signage, retro candy, cute festival masks. Definitely a fun place.
And while the soup looks simple, it is rather deep.
Their menu claims that their kodawari lies in three parts; noodles, soup, and heart. The soup was a highlight. Taking about 10 hours to make, it's rich and deep. The noodles are homemade with Hokkaido flour. And the heart? Just looking around at the families slurping away in this retro shop made it clear that, yes, that is as important as the taste.
The menu has many bowls, but the simple kakesoba let's you savor just the noodles and soup.
Official site here.
Kanagawa-ken, Atsugi-shi, Saiwaicho 9-6
Closest station: Hon-Atsugi
Open 11:00-15:00, 18:00-23:00