(*Note: This is an in-game legend and has no historical parallels)
Tatsunoshin Suou is a well-respected samurai during the Period Of The Warring States, and vassal to the feudal warlord Kiyotada Sumaru. Disgusted by how his tyrannical lord rules the country, Tatsunoshin set out to assassinate Kiyotada with the help of his ninja servant Junnosuke Kuroda and lover Maihime Amano. Though Kiyotada was incapacitated, the move ended in tragic failure when Maihime was killed in battle.
In an act of desperation, Tatsunoshin instructs Junnosuke to set fire to Sumaru Castle and escape with his life. Tatsunoshin stayed inside the burning structure with the body of his beloved, swearing to exact his true revenge someday.
Prior to entering Sumaru Castle, a rumor can be obtained from Akinari Kashihara regarding the existence of Tatsunoshin Suou's mummified remains. If the rumor is spread, the mummy will appear in one of the rooms of Sumaru Castle and will acknowledge Tatsuya and Katsuya as his descendants. Afterwards, Tatsunoshin Suou can be summoned as a Persona of the Sun Arcana.
Similar to Katsuya Suou in the Japanese version, Tatsunoshin Suou's surname can be changed if the player imports the save data of Innocent Sin with Tatsuya Suou's surname changed before starting a new game of Eternal Punishment.
In a darker note, it is implied the legend of Amano, Suou, Kuroda and Sumaru is a fake spread by Nyarlathotep, to induce the party to alter history with rumors of a past that never happened.
His legend could be based on the Honnoji Incident, where Akechi Mitsuhide, a retainer of Oda Nobunaga, betrayed him and killed him by setting fire to a temple. Unlike Mitsuhide, however, Tatsunoshin Suou is seen as one that fought for the freedom of his people and killed Kiyotada because he saw him as a tyrant. Meanwhile, the reasons for Mitsuhide's betrayal are unknown, but it could have happened because Mitsuhide wanted to usurp Nobunaga.