Seishirou Sakurazuka

Seishirou Sakurazuka is the main antagonist of Tokyo Babylon and supporting villain of X. It's revealed from X that he is one of Dragon of Earth.

In Tokyo Babylon OVA, he was voiced by Takehito Koyasu in Japanese version and Dean Fenton in English version.

In X/1999 series, he was voiced by Otoya Kawano in TV series, Tōru Furusawa in feature film in Japanese Version and Dave Mallow in TV series, Garrick Hagon in feature film in English Version.

Personality
He appears as a kindly veterinarian often showing romantical affection to the young onmyoji Subaru Sumeragi.

Early Life
A sidestory in the series also shows Seishiro becoming the Sakurazukamori by killing his mother, Setsuka. As she dies in his arms, she tells him he will also be killed by the person he loves.

Tokyo Babylon
After become the Sakurazukamori, Seishirō was supposed to kill the young Subaru when being found by him. Impressed with kid's purity, Seishirō made a bet with him: Should Seishirō come to love him after living a year with him he would spare him and otherwise he would kill him. As a result, he almost kills the young onmyōji, but Subaru's grandmother intervenes to free him from the illusion, leaving herself crippled as a result.

Years later, Seishirō appears as a veterinarian working in Shinjuku, Tokyo. He is friends with the meets up with 16-year-old Subaru Sumeragi, Japan's most powerful onmyoji, after the latter's shikigami causes an unlikely meeting between the two at Ikebukuro train station. Seishirō begins a year of courtship that will ultimately change both of their lives. Often he professes his love for the boy, with Subaru's eccentric twin sister Hokuto enthusiastically supporting the pairing, much to Subaru’s embarrassment.

Seishirō also protects Subaru on several occasions, even sacrificing his right eye to protect Subaru from a knife-wielding attacker.

Though freely sharing his knowledge of the occult and occasionally using his powers, Seishirō obscures his true identity and personal details. After a year passes and Subaru finally realizes his love for Seishirō, but at this point Seishirō reveals he is the Sakurazukamori, Japan's top one assassin.

Seishirō disappears from Subaru's life after this point; Hokuto, fearing that he will come after her brother, offers up her own life in his place. Seishirō accepts and stabs her through the heart; with her last breath

X
After leaving Tokyo following the events of Tokyo Babylon, Seishirō returns to the city to assume his place as one of the Dragons of Earth, one of the warriors destined to fight against the Dragons of Heaven to eliminate mankind. He encounters Subaru and other Dragons of Heaven while destroying one of the city's barrier but their fight does not conclude. Though still unemotional, Seishirō makes an unlikely friend with Fuuma Monou, the most leader of the Dragon of Earth, who while taking one of Subaru's eyes in combat tells him that only Seishirō can grant Subaru's true wish.

Seishirō encounters Subaru for one final fight in the Rainbow Bridge. After some time of fighting, Seishirō heads in for the finishing blow. Hokuto's final spell takes effect, leaving Subaru with his hand through Seishirō's chest, killing the Sakurazukamori instead. Hokuto's final wish was Subaru could not be killed the same way she was. Seishirō knew this, effectively committing suicide as Fūma states Subaru's wish was dying at Seishirō's hands. After the battle, Fūma offers Subaru Seishirō's remaining intact eye, revealing that it was Seishirō's wish to erase Fūma's trace on Subaru, which Subaru accepts. This act completes this ritual and, after regaining his full sight, Subaru becomes the 14th Sakurazukamori and one of the Dragons of Earth.

Trivia

 * Seishirō was created alongside Subaru and his twin sister Hokuto as the main characters for a dōjinshi novel. After undergoing major changes, he was used as one of the main characters from Tokyo Babylon. Ever since his introduction in Tokyo Babylon Seishirō has been well received by publications for manga and anime for his relationship with Subaru which would transform into one of the most famous rivalries from X.