The Tenjuin Mausoleum is final resting place of the daimyo Mori Terumoto (1553 to 1625) and his wife, known both as Seikoin and Lady Minami no Okata. "Tenjiuin" is Mori Terumoto's posthumous name, and the mausoleum sites on the site of his former residence. Terumoto's loyal retainer Nagi Motofusa is also interred here. Motofusa committed ritual suicide following the death of his lord in 1625.

The Mausoleum is humble compared to the grandeur of two other Mori family memorial sites in Hagi, the Daishoin and Tokoji temples. The Tenjuin Mausoleum once had a temple as well, but it was destroyed in 1869. The graves of Terumoto and his spouse, a pair of five-tier gorinto stone towers, are surrounded by a stone fence. A stone torii gate stands at the entrance, and stone lanterns line the 64m path to the mausoleum.