Why is the sun shining along the inland sea coast of Seto?

Seto Inland Sea Seto Inland Sea, Japan. Located between Honshu, Shikoku and Kyushu, Japan. There are Shikoku Island in the southeast and Honshu Island in the northwest. Both islands are mountainous, and the inland sea is located in the East Asian monsoon region, with southeast wind prevailing in summer and northwest wind prevailing in winter. The two islands are like two walls blocking the southeast and northwest directions, so that the Pacific water vapor brought by the southeast wind and the Japanese sea water vapor brought by the northwest wind are blocked by the two islands. The inland sea area has always been in the rain shadow area of leeward slope, so the precipitation is relatively small. Therefore, the climate along the inland sea of Seto is warm, rainy and sunny.