Saturnus (サトゥルヌス?) or Saturday (サタデー?) is a recurring demon in the series.
"The Roman god of agriculture. He is commonly identified with Cronus. In an attempt to prevent his destiny, he ate his children, but was overthrown as was fated."
Known as Saturn (Latin: Saturnus) the Roman god of agriculture and harvest. In ancient times, he was known for being the Roman god of agriculture, justice and strength. Saturnus is also identified as Cronus, the leader of the Titans from Greek mythology. He is the namesake for both the planet and Saturday. His mother was Gaia and his father was Ouranos. He was identified in classical antiquity and is famous for castrating Ouranos using a sickle, which lead to the birth of Venus.
Saturnus is the Persona representing the bond between Yu and Teddie. He was first summoned during the battle against Kunino-sagiri to protect Yu from fire attacks. However, Kunino-sagiri was able to possess Yu while still using Saturnus, who unleashed a barrage of Agidyne attacks on the team. Luckily, his attacks were blocked by Konohana Sakuya.