Suo-Ohshima Island of Yamaguchi Prefecture is the third largest island in the Seto Inland Sea.  Suo-Ohsima is connected with the main island by Oshima Ohashi Bridge.  The Island is well known as a tangerine-producing island thanks to a moderate climate throughout a year.  As well as having a rich environment, Suo-Ohshima has abundant historical and cultural resources such as the landing monument of Siebold, the museum of battleship Mutsu, and the museum of Tsuneichi Miyamoto, one of the greatest cultural anthropologist in Japan who was the native of this island.  

The sea around Suo-Ohsima Island is a habitat for finless porpoises that are at the top of the food chain in the Seto Inland Sea.  We visit the observation points by vessel.  (We go to these points based on our data, however, we are not always able to see finless porpoises.)  Off the south coast, from Jikamuro to Kominasejima Island, Japan's largest coral beds (Alveopora japanica) occur.  Divers dive into the sea and shoot coral images using an underwater camera and we see the live images onboard the vessel.

The old trail from Jikamuro to Tononyu is a wonderful trekking trail.  History and culture are blended with nature.  There are various old tales and kaidan (scary stories) associated with the trail.  We can also see strange-looking rocks along the trekking course.

Nakajima Island has the largest population and area among the Boyo islands.  The history of this island is old and aliases of this island are found in several ancient documents.  From the Namboku-cho period to Sengoku period, the island was the base of Kutsuna, a local ruling family who had a suigun force.  However, after the unification of Japan by Toyotomi Hideyoshi, Nakajima Island became an island of agriculture and maritime trading.

At Kuwana Shrine on Nakajima Island, more than 40 ema are preserved.  The motifs of ema belong to Kuwana Shrine are mostly ships based on the island's history.  Most of the ema are wooden plaques and were made during the Edo Period.   It is considered that a ship motif ema represents the history of the Kutsuna family and maritime trading with wakou.  Therefore, these ema are precious for research on transportation and trading in the Seto Inland Sea area.

Ohminasejima Island has been uninhabited for about 50 years.  Before World War II, there was a schoolhouse.  There was a barracks during the war, and after the war the island was a residential area for demobilized veterans.  However, the island is now covered with deep forests although we can see ruins of wells and shrines.  Due to the lack of guji (chief priests of Shinto shrines), rituals are no longer conducted and cultural and historical inheritance is on the verge of a crises.  

On ecotours we observe plants, wild birds and lava as part of the activities.  

Seto Eco conducts environmental learning for primary school students.  Since 2015, we have conducted environmental learning courses focusing on finless porpoises and coral observation for 5th and 6th grade students of Kihara Primary School in Mihara City.  For watching finless porpoises, we visit observation points by vessel based on porpoise location data we collected and transmitted.  The aims of this project are to raise children' awareness about nature conservation and improvement through environmental learning programs, such as nature experience.  Divers go into the sea and shoot coral images using an underwater camera and children see the live images on the vessel.  Seeing the underwater world and ecology of corals is a unique experience that we can provide.  We also conduct observations of intertidal organisms, sea plants and birds as part of the uninhabited island experience.