Tsubaki Kasugano (春日野 椿, Kasugano Tsubaki) is the Sixth diary owner. Tsubaki is the High Priestess and Oracle of the Omekata Religion. Her followers know her as the Sacred Eye because of her supposed powers of clairvoyancy, although this was actually granted to her by her Future Diary, the "Clairvoyance Diary".
Tsubaki (or sometimes refered to the sacred eye) is the holder of the Thousand Leagues Eyes Diary [or the Clairvoyance Diary (千里眼日記) in the anime] which is a scroll that records what her followers see. This reflects the line "the only joy in life is writing down the stories of my visits in my diary"(or in the ep 4 omake "recording the reports from so many of my followers is a lot of work").
Tsubaki is a pretty young woman, but has poor vision, leading her to spend her entire life living in the Omekata temple. She has long dark blue hair, some of it pinned up with a butterfly-shaped hairpiece, while the rest hangs loose, part covering the right side of her face. She wears a red kimono.
Tsubaki is introduced as a polite, considerate and friendly girl who fears for her life and requests that Yukiteru Amano becomes her guard until the time for her predicted Dead End passes. She is quite intelligent and relies on her own intuition, believing Yuno Gasai will be Yuki's undoing. She forms a friendship with Yuki, describing him as cute and harmless. However, she forms a tense rivalry with Yuno, both trying to pull Yukiteru from one direction to another.
When Tsubaki's backstory is revealed, so are her true colours. Bitter, angry and emotional, Tsubaki really hates the world, the Omekata religion and her life, planning to become God to destroy the world and recreate it. She is quite manipulative, having manipulated Yuki, Yuno, Keigo Kurusu, Minene Uryu, and Yomotsu Hirasaka into coming to the temple in order to eliminate all of them easily. She falsifies her damsel in distress act to easily lure in Yuki, using his habit to quickly trust people against him. Upon revealing her true self, she thanks Yuki for protecting her and then gives him a crude kiss just to watch Yuno squirm.