It is said that Kobo-Daishi (or Kukai), the founder of Shingon Buddhism (the esoteric school of Buddhism specific to Japan), himself built this temple in 825 (a few years after Dainichibo Temple). With Dainichibo Temple, they constitute the pillars of the Shingon Buddhism practice around Mt. Yudono.
This is where you will find Tetsumonkai's mummy, the most famous sokushinbutsu of them all. Tetsumonkai was born in 1789 and died in 1830 at the age of 71. He entered Churenji Temple at the age of 21. Feeling remorse for his past crimes (he murdered two soldiers as an act of self-defense), he chose to serve the people by becoming a Buddhist monk. He led his training further by undertaking the sokushinbutsu training, which he successfully accomplished to the end.
Apart from the mummy, you will find a strange pop-art ceiling with dozens of pop culture icons painted in bright colors, and a 200-year-old Sakura tree: the Shimekakezakura.