Sumaru Castle (珠閒瑠城) is a dungeon found in Persona 2: Eternal Punishment. It is shaped like an old-fashion .
According to the in-game legend (actually a rumor manipulated by Nyarlathotep), Sumaru Castle was burnt down to the ground during the conflict between Kiyotada Sumaru (Gozen), Tatsunoshin Suou, Maihime Amano and Junnosuke Kuroda in Warring States.
In the actual event of the game, when Torifune, the gigantic spaceship underneath Sumaru City, lifts the whole city into the air, Sumaru Castle emerges from the underground of Honmaru Park where Kiyotada Sumaru's mummy (head only) was unearthed by the New World Order executives decades ago. Tatsuzou Sudou with his New World Order executives arrives at the Utena (roof terrace) of the castle to prepare the Dragon Ritual in order to release the Kegare. This act will enrage the Earth Dragons across the world to ascend from the underground, causing .
A puzzle related to the(Ursa Major) is blocking player to access the Utena. It requires the player to collect 7 "Kotodamas" (characters) from the 7 lithographs scattered within the castle. Combining the 7 Kotodamas correctly according to the order of the lithographs which represented by the stars of the Big Dipper will result in a mythological figure's name to access the locked door at 2/F to Chamber of Henbai.
The figure differs between Japanese and English versions. In the Japanese version, it is Sonjōō (ソンジョウオウ / 尊星王, lit. "Lord of the Respectful Star"), the alternative name of Polaris. The English version replaced it with , the Greek hero who slew Medusa. Perseus was picked for this replacement probably due to is located in the northern sky, which the Big Dipper is commonly known as the "Seven Stars of the North Dipper" in Taoism. Either way, Katsuya Suou finds it ironic the puzzle correlates figures from different religions or mythologies, and wonder if this is due to the power of rumors., the Shingon Buddhist Bodhisattva. He is related to this puzzle because Sonjōō represents
Behind the locked door is the second puzzle which requires player to walk in the specific path of "Henbai" to reach the other door. The pattern is hinted by the golden lithograph "Form of Reverse Souryu Henbai" next to the entrance. The larger circles on the floor also mark the turning point of the path.
When the player party has reached the chamber of Utena, they find that Tatsuzou has slain all four New World Order executive as sacrifices for Gozen to initiate the Dragon Ritual. The Earth Dragons soar to Torifune, leaving severe ground fissures behind from where they ascend. Tatsuzou is then transformed by Gozen into Detested Hunter, a deformed demon. After Tatsuzou's defeat, Gozen is awakened as a four-legged monster to conquer the player. The death of Gozen results in the outer rims of Torifune and the Earth Dragons to be crushed and the floating city is absorbed into the Collective Unconsciousness. The player team is teleported to Monado Mandala, greeted by Nyarlathotep itself.
If the player has completed the prerequisites to obtain the ancestral Personas of Tatsunoshin Suou, Maihime Amano and Junnosuke Kuroda, Maihime can be found on 3/F and the other two on 7/F. They will give the player access in the form of Personas to be summoned in the Velvet Room, without the need of Material Cards, which are usually required to summon special Personas.