|Series||Shin Sakura Taisen|
|Koubu||Spiricle Fighter Mugen|
|Shin Sakura Taisen|
|Japanese Voice||Yohei Azakami|
In his youth, Seijuro would spend his time playing with his childhood friend Sakura Amamiya around her home. Usually one of their activities involves playing with their 'sacred' wooden swords given to them by Sakura's father Tekkan. After Sakura told Seijuro her dream of becoming a Flower Division member, the boy would make a promise that he will become captain of the Flower Division so that he can protect her. Happy that Seijuro made this promise, Sakura also asks if Seijuro could promise to marry her once they're older, which the boy agreed.
As Seijuro grew older, his family would move away and he eventually has forgotten both of his childhood promises with Sakura. He would later study at an academy to become a naval officer, where he met and became good friends with Reiji Shiba. When Reiji was depressed after finding out he has no spirit energy to power up a spiricle striker, Seijuro convinced him not to let his dream end there and unknowingly inspired his friend to become an engineer instead.
By the time Seijuro joined the navy, he was appointed as captain of the Marishi-ten. The young captain would take his crew and ship out on several missions until a fateful day when a passenger ship was attacked by demons out in Tokyo waters. Seijuro performed his best to ensure the safety of his passengers and crew by using his ship as decoy, but the Marishi-ten soon sank due to not being equipped to deal with demons. It was the Shanghai Combat Revue that rescued Seijuro, his crew, and the passengers from the demons on time before any casualties happened.
Due to what happened with Seijuro's fiasco attempt to save civilians, his naval superiors eagerly accepted Sumire Kanzaki's request for him to transfer to the Imperial Combat Revue so that he can become captain of the Flower Division. Though depressed that his dream of being a naval captain is over, Seijuro would put his worries behind and look ahead to what his next assignment will be.
In the games
With the hack-and-slash game mechanics introduced to the 2019 game, Seijuro performs as both a dual-sword fighter and the player's fixed character unit in battle.
Mugen-Class Spiricle Striker
- HP: 9
- Attack: 7
- Defense: 7
As captain of the Flower Division, his playstyle is the most offensively well-balanced among his fellow melee allies. The player can make easy use of his dual swords and the Mugen armor to finish off enemies with ease at their own pace.
His fast attacks are like Sakura's, but with an extra slash to put more ferocity and speed into strikes. He can also perform a spinning slash on the third fast strike to protect him from behind as well before moving on to his fourth consecutive hit.
Seijuro's basic strong attack allows him to perform a cross slash with his two blades that can knock his enemies back, and his strong dash attack offers three rotational slashes through his foes. In combination with his fast strike combos, Seijuro's strong attack can perform a ground stab with his swords to electrify his enemies around him. In chain with the second fast attack, he can pierce his foes with his swords, and he can use a strong launch to lift his opponent in the air after the third strike. Once Seijuro reaches his fourth and final fast strike, his strong attack can become a jump strike that also electrifies his foes around him when he lands.
For Seijuro's mid-air moves, he can make consecutive slashes with his fast attacks, or perform a vertical cartwheel with his swords to bring him straight down and making a splash of electricity. Given that he can slash vertically in his strong attack state, it can be useful for clearing enemies beneath him or damaging tall enemies.
Since Seijuro is fixed into every battle map in the game as the main protagonist, players can find him easy to use with his Mugen's attack speed and combos compared to Sakura Amamiya's Kobu Type-3. His role as a fixed melee character helps to balance out with the other members' playstyle as well, allowing the player to switch between characters for the occasion during the battle.
While Seijuro is the most balanced when it comes fighting close-quarters, his weaknesses include enemies that can attack him from a long range as he will need to get close to attack them. He is also not infallible to getting countered when fighting stronger enemies and bosses so players will need to make efficient use of his dodging to avoid overextending themselves.
Seijuro's special attack, Crossblade Tempest, is a combination of most of his fast and strong attack combo animations. Like all specials, he remains immune to getting attack as he continues to slash at his foes. By controlling where he moves, his sword strikes in this state can either wipe out all enemies around him or even focus all the damage at one target that can even kill giant foes like Hellfiends. Seijuro's Crossblade Tempest can easily devastate and KO most bosses' health, even without requiring a team attack to give him an offense boost to his damage.
- The name Seijirou means "sincerity" (誠) (sei), "ten" (十) (ji) and "son" (郎) (rou).
- Seijirou's surname Kamiyama means "god" (神) (kami) and "mountain, hill" (山) (yama).