This manhole cover is from the town of Hagi in Yamaguchi Prefecture. It depicts 2 of the things this popular tourist destination is famous for, old walls, and Natsumikan. The natsumikan is a type of large, bitter orange that bears fruit in the summer. You can see many natsumikan trees throughout the town, and juice and preserves from the fruit are on sale everywhere.
Large sections of Hagi have been spared redevelopment, mainly as a result of the railways line going around the town rather than through it, so some areas of the town are still laid out as they were in the Edo period. Tall earthen walls and stone walls in a multitude of forms line the streets.
Utilizing old rooftiles in walls is not uncommon. See this one in Kyoto.