Taira no Masakado was a samurai during the Heian period in Japan. He led a small but thriving rebellion to capture three provinces - Hitachi, Shimotsuke and Kouzuke - now known as the Kanto region's Ibaraki, Tochigi and Gunma prefectures respectively. As a response to the rebellious member of the Taira clan, the Kyoto central government at the time announced the bounty on his head. At the Battle of Kojima occurring eastward of Kanto, Masakado was killed by Fujiwara no Hidesato and Taira no Sadamori, his cousin. His head was brought to Kyoto, and later to Edo where it was buried. Here he is regarded by the locals as a demigod, and a belief persists that the conditions of his shrine dictates the fortune of the metropolis.
After the great flood, the player can visit the dwelling place of Masakado on a solitary island, if they are following the Neutral path. He laments the destruction of Tokyo between the warring factions, and bestows his sword to the player.
Shin Megami Tensei II
Masakado is first mentioned upon Aleph's arrival to Roppongi, where he is greeted by Masakado's servant, Hiruko. According to Hiruko, Masakado's body is currently torn to six-pieces as a fell victim to the internal conflict between the Yamato Gods, and thus, Hiruko requests Aleph to break the seals sealing the six pieces of Masakado's body, and retrieve them so Masakado can be resurrected.
Upon retrieving all of Masakado's separated body, Hiruko will then prompt Aleph to fuse all Masakado's body and resurrect him at the Jakyo Manor. However, as Aleph only retrieved Masakado's body parts, but not his soul, the fusion of Masakado's body creates the soulless form of Masakado, in which Hiruko later informs Aleph that Masakado's soul is crucial to fully resurrect Masakado, and reveals that he actually holds Masakado's soul. Congratulating Aleph's efforts of retrieving Masakado's body parts, Hiruko bestows Masakado's soul to Aleph, allowing the fusion practitioner to fuse Masakado's soul to his body, fully resurrecting him.
As a gratitude for resurrecting him, Masakado grants Aleph the item Sun Pillar and Katana of Masakado, and helps Aleph in breaking the seal in the Sealed Cave, which Aleph must then free the Amatsukami clan sealed inside. Masakado later informs Aleph that due of his recent awakening, his powers are not fully healed yet, and thus needs rest for to recover his strength, bidding farewell to Aleph.
In the Neutral Alignment route, Katana of Masakado later helps Aleph in banishing the guard demons guarding Lucifer's Castle Kether.
Shin Megami Tensei III: Nocturne
Masakado makes a cameo appearance in Shin Megami Tensei III: Nocturne. If the Demi-fiend manages to collect all of the 24 Magatama scattered around the Vortex World, the minister of the Cathedral of Shadows will give the Demi-fiend the "Lord's Blade", advising him to visit the grave of Masakado with the sword in his possession. Upon examining the gravestone, the blade will react, and the Demi-fiend will find himself teleported to the Bandou Shrine.
After lowering the pillars and defeating all four Devas, the Demi-fiend can finally approach Masakado, who proceeds to question the Demi-fiend's purpose. Regardless of the answer, Masakado will impart his power to the Demi-fiend in the form of the Magatama Masakados. It is all he can do since he cannot exist in the world outside.
Masakado also tells the Demi-fiend that regardless of what kind of world Tokyo would turn out to be, it is still Tokyo. As the current bearer of his power, the Demi-fiend will now protect Tokyo in Masakado's stead however the Demi-fiend sees fit.
If the player re-enters and speaks to Masakados again, Masakados is seen encouraging the Demi-fiend to journey forth and conquer the multiverse and further encourages the Demi-fiend to choose how he best feels Tokyo should be protected.
Shin Megami Tensei: Strange Journey
"A general who declared himself the new emperor of Japan, but fell to Hidesato Fujiwara and Sadamori Taira. He was enshrined to quell his spirit, and later became known as the protector god of Kanto."
"A general who declared himself the new emperor of Japan, but fell to Hidesato Fujiwara and Sadamori Taira. He was enshrined to quell his spirit, and later became known as the protector god of Kanto. According to the Otogizoshi, he was over 210 cm tall, had a body made of metal, and had two pupils in his left eye. However, he had a weakness: his temple was still made of flesh."
—Shin Megami Tensei IV Profile
Masakado is a key figure in the story and is central to the Neutral route ending. His sword is carried by Skins, who cannot unsheathe it. If Flynn does not side with Jonathan, Walter, or the White, Skins will pass down the sword to him when the latter speaks Masakado's name and is able to unsheathe the sword. It turns out that Masakado has fallen silent after doing battle against the angels long ago. By drawing the sword in front of the monolith in Ginza, Masakado's soul is awakened once again. Masakado refers to Flynn as the reincarnation of someone familiar to him. In the neutral ending, after Flynn has completed Masakado's quest to recover his body, Masakado lifts up the Firmament between Tokyo and Eastern Kingdom of Mikado, destroying Mikado and returning the sky and sunlight to Tokyo.
In one of the DLC missions, it is revealed by Stephen that Flynn's former self accompanied Masakado to defend Tokyo from the ICBM attack 25 years ago. Masakado took the form of a gigantic being to be the shield, but by doing so he went berserk and threatened to destroy Tokyo. Flynn's former self had no choice but to attack Masakado until he came to his senses. Masakado's body then steadily fell down and covered the entirety of Tokyo and his back was later used by the angels to construct what would become the Eastern Kingdom of Mikado.
Devil Summoner: Soul Hackers
"A general who declared himself the new emperor of Japan, but fell to Hidesato Fujiwara and Sadamori Taira. He was enshrined to quell his spirit, and later became known as the protector god of Kanto. According to the Otogizoshi, he stood over 6'10", had a head, arms, and legs of gold, and had two pupils in his left eye. His body was made of iron, but his temple was his only weak spot."
—Devil Summoner: Soul Hackers 3DS Compendium
Masakado can be obtained if Zeed is level 80 or above and fused with Hachiman during a new moon.
Devil Summoner 2: Raidou Kuzunoha vs. King Abaddon
Masakado will only be available on New Game Plus after completing 103% of the case files in the game; this requires completing the Chaos Path and beating the New Game Plus ones given by Louis Cyphre you get from the Chaos playthrough. A man named Soma will be near the Narumi Detective Agency and gives the case file.
Masakado is on the 999th floor in the Confinement Chamber. The anger and rage that fuels him will soon make it possible for him to be free. He is joined in battle by an Impostor Masakado, who is weak against all four elements. A new Impostor spawns after each defeat but only so many times. Masakado uses the bad luck roulette greatly to his advantage. Among the many things the roulette will use against Raidou is to reflect all damage on Masakado, reducing Raidou's stats to 1, null all elements but almighty, kill all summoned demons, etc. Using Luck Locusts will cancel these effects. After a certain amount of damage Masakado will randomly teleport around three spots on the field and will use one of his attacks after teleporting.
After his HP has dropped to zero he will stop moving, Raidou must then negotiate with him to end the battle. After the battle it is revealed that Souma is Masakado and he thanks Raidou for defeating his hatred, which had run amok thanks to the negative energy influencing the capital. Raidou's rewards is the Blaze Steel and the ability to fuse Masakado. Masakado can be fought more if Raidou wishes to get more Blaze Steels.
Persona 3 / FES
Masakado appears as a Persona of the Tower Arcana in Persona 3. He can only be summoned by obtaining the key item Masakados, which can only be obtained by completing all of Elizabeth's Persona Fusion requests. In reference towards his role in Shin Megami Tensei III: Nocturne, Masakado's fusion prerequisite requires the protagonist of perform a cross-spread fusion consists of Zouchouten, Komokuten, Jikokuten, and Bishamonten in the Velvet Room. Masakado also grants the equipment Masakado's Hair, which heightens the occurrences of evading physical attacks.
In Persona 3 FES, the strongest two-hand sword, Katana of Masakado can also be obtained by fusing Masakado with a Nihil weapon in the Antique Shop via the Weapon Fusion system. The item itself is from #52.
Persona 4
Masakado returns as a Persona of the Tower Arcana in Persona 4. He can be summoned once the protagonist reaches Lv 69 or above and by fusing the appropriate Persona.
Devil Survivor 2
"A general who declared himself the new emperor of Japan, but fell to Hidesato Fujiwara and Sadamori Taira. He was enshrined to quell his spirit, and later became known as the protector god of Kanto."
—Devil Survivor 2 Compendium
Masakado appears as the strongest member of the Hero race. He can only be obtained by fusing Amaterasu and Yoshitsune.
Tokyo Revelation
Kojiro is the reincarnation of Masakado, both Gagyson and a secret order that watches him fear his awakening as it will not only foil Ose's revival, but also lead to great destruction across the earth. Later, in order to save Kojiro's life the young witch Kyoko reincarnates him. Masakado then defeats the demons threatening to kill his brother and Cerberus, and together with Cerberus faces off against Ose. Though easily beating Ose, thanks to letting his guard down Ose knocks Cerberus out and catches Masakado, but is able to free himself and continue fighting Ose. After Akito reincarnates Saki as Konohana Sakuya, Masakado defeats Ose for good by unleashing an attack that incinerates him completely. Exhausted from the fight, he is caught by Konohana Sakuya as he falls and turns back into Kojiro.