Onomichi is a gritty, old-timey seaport town with hills full of temples and literary sites. Film director Ōbayashi Nobuhiko was born in Onomichi, and the town has featured in a number of Japanese movies, notably Ozu's Tokyo Story. It's also known for its rāmen, and you'll find plenty of places dishing it up.
About 6km inland from Nima Station on the San-in coast west of Izumo is the old Iwami Ginzan silver mine, a Unesco World Heritage Site. In the early 17th century, the mine produced as much as 38 tonnes of silver annually, making it the most important mine in the country at a time when Japan was producing around a third of the world's silver every year.
About an hour away from Hiroshima by train or bus, Iwakuni makes for a worthwhile half-day trip, or a stop-off en-route between Yamaguchi and Hiroshima. The main reason to come here is to see the five-arched bridge Kintai-kyō, and take a walk around the Kikkō-kōen area to which it leads. It's also possible to watch traditional cormorant fishing here during the summer.
The Bizen region has been renowned for its ceramics since the Kamakura period (1185–1333). The pottery produced here tends to be earthy and subdued, and has been prized by dedicated tea-ceremony aficionados for centuries. Travellers with an interest in pottery will find the gritty Bizen town of Imbe (伊部) and its kilns a worthwhile side trip from Okayama.
Although it's not one of Japan's highest mountains, at 1729m Daisen looks impressive because it rises straight from sea level – its summit is only about 10km from the coast. Daisen is part of the Daisen-Oki National Park (大山隠岐国立公園). The popular climb up the volcano is a five- to six-hour return trip from Daisen-ji temple.
A short train ride east of Hiroshima is the town of Saijō (西条), where seven sake breweries are clustered within easy walking distance of the station. The brewers here know their stuff – Saijō has been producing sake for around 300 years – and most open up their doors to curious and thirsty visitors for free sake tastings.
North of Matsue in the Sea of Japan are the remote and spectacular Oki-shotō, within the Oki Islands Geopark, and with coastal areas that are part of the Daisen-Oki National Park (大山隠岐国立公園). These islands were once used to exile officials (as well as two emperors) who came out on the losing side of political squabbles.
If there's not enough to inspire you on Naoshima, get yourself across to Teshima (豊島), a small island between Naoshima and Shōdo-shima with a number of art sites. A highlight is the Teshima Art Museum, which is really just an enormous concrete shell, forming a low tear-drop-shaped dome on the hillside.
Located between Kurashiki and Fukuyama, the port of Kasaoka is the jumping-off point for six small islands connected to the mainland only by boat. In particular, the islands of Shiraishi-jima and Manabe-shima are worth visiting to enjoy the slower pace of life as it used to be lived all over the Inland Sea.
The mountainous island of Ōmi-shima is connected by bridge to Ikuchi-jima to the east and Ō-shima to the west. It is home to one of the oldest Shintō shrines in western Japan, Ōyamazumi-jinja, near Miyaura port. The deity enshrined here is the brother of Amaterasu, the sun goddess.
Sleepy Shiraishi-jima is popular in the summer for its beaches and there are some good walking paths. Go-everywhere Buddhist saint Kōbō Daishi stopped off here on his way back from China in 806; the temple associated with him, Kairyū-ji, incorporates a trail of small shrines leading to a huge boulder on top of the hill.
Three stations south of Nima is the coastal onsen town of Yunotsu, one of the ports from where silver from the Iwami Ginzan mines was shipped to the capital and beyond. Now a protected historic area, it consists of a couple of narrow streets of well-preserved wooden buildings and two atmospheric public baths where you can soak up the mineral-rich waters with the locals.