Shinjuro Rengoku

Shinjuro Rengoku is the father of Kyojuro Rengoku and Senjuro Rengoku and the husband of Ruka Rengoku. He formerly served as the Flame Hashira of the Demon Slayer Corps.

Appearance
Shinjuro strongly resembles his sons, Kyojuro Rengoku and Senjuro Rengoku, possessing unruly orange hair that flares out around his face, becoming redder near the ends above his ears, that he wears messily tied back behind his head. He has fair skin, bushy black eyebrows and bright, orange eyes that redden near the pupils, that are slanted inwards and shaped so as to give him a furious appearance.

Shinjuro wears a traditional kimono robe. When he was the Flame Hashira, he also wore the haori with flame-like ridges at the end that Kyojuro wore when he was the Flame Hashira. In the Infinity Castle Arc, he is shown with a katana with a flame guard similar to Kyojuro's, with what appears to be a flame pattern on the sheath.

Personality
Shinjuro is a very short-tempered man, especially when regarding the Demon Slayer Corps and his son, Kyojuro, with the mention of either causing him to grow furious. He appears to be abusive, harshly insulting the recently deceased Kyojuro and knocking Senjuro to the ground during his fight with Tanjiro. He is also an alcoholic - his first action upon awaking after being knocked out by Tanjiro is to buy alcohol, and he is often seen drinking with sake.

Shinjuro possesses feelings of inferiority, which stemmed from reading the chronicles of the past Flame Hashira, where Sun Breathing is described as the original and most powerful breathing style. He mocked the other styles as "cheap imitations" of Sun Breathing and accused Tanjiro of coming to their residence to mock them for his superiority, after recognising his Hanafuda earrings.

However, it is later revealed that Shinjuro truly cared for Kyojuro despite what he said to Tanjiro, and the memory of Kyojuro causes Shinjuro to begin breaking down in tears.

He later defends Kiriya and the rest of the Ubuyashiki Family with Tengen Uzui and vows to follow Kyojuro's example and not to bring shame to the Rengoku family.

History
After his wife's passing, Shinjuro began drinking while doing duties as a Hashira and eventually encountered Hairo who he, in a drunken rage, proceeded to cut various parts of his body without ever cutting his head whilst lamenting on why his wife had to die yet Hairo, a demon, managed to survive and that he sees that all the things he's done as utterly pointless and proceeded to tell Hairo that he was a coward despite being a demon and questions him if he really wants to keep escaping like a coward until he dies.

He once saved a young woman and her daughter from being harmed by a demon, using Flame Breathing, First Form: Unknowing Fire. That woman would remember his actions once more when she and her granddaughter was saved again by Kyojuro.

Shinjuro saved a young Obanai Iguro from the Serpent Demon and reunited him with his cousin. Nonetheless, due to his cousin's attitude, Shinjuro had to separate them.

Before retiring as the Flame Hashira, Shinjuro tore apart the Generational Flame Hashira Record of the Rengoku family.

Mugen Train Arc
In Kyojuro's Blood Demon Art-induced dream aboard the Mugen Train, Shinjuro first appears, lying on the floor of their house and gazing out of the open doors at the garden. Kyojuro remembers that he's supposed to have just reported to him that he has become a Hashira and his father, unimpressed, says that it was pointless because neither himself nor Kyojuro can ever become great people.

Kyojuro recalls that Shinjuro wasn't always this dismissive and that he used to be a man of great skill and passion for demon slaying, but suddenly, one day, the man, who had raised himself and Senjuro Rengoku so passionately, simply gave up on the blade.

Shinjuro appears once again after the battle with Enmu, Lower Rank One of the Twelve Kizuki, and Akaza, Upper Rank Three. He suddenly appears from his house, yelling that what Tanjiro's come to tell them is useless and belittling and cursing Kyojuro for becoming a Demon Slayer since he always knew it would just get him killed. Tanjiro and Senjuro are shocked by his words, but remain silent as he continues to rant about how people's powers are already decided for them at birth, but Kyojuro still went and became a Demon Slayer despite the fact that he had none. At the sound of these sharp words, tears begin to form in Senjuro's eyes, but, instead of stopping and comforting his son, Shinjuro tells him to stop making that pitiful expression since the funeral is already over. Angered by this display of cruelty, Tanjiro asks Shinjuro to stop talking to and about his sons in that way, which only causes the latter to turn his attention to him and yell at him to get off his property, and, defiantly, Tanjiro says that he is a Demon Slayer.

The container Shinjuro is holding smashes to the ground as he considers what this could mean, and, jumping to the first conclusion that comes into his mind, he angrily asks Tanjiro if he is a Sun Breathing user. Without waiting for an answer, Shinjuro swiftly attacks Tanjiro and pins him to the ground, forcefully slapping Senjuro away when he tries to pull his father off the injured Demon Slayer. While Shinjuro is distracted by his son, Tanjiro swiftly delivers a blow to his face, forcing him off of him, and, as Tanjiro's patience has finally worn thin, furiously asking him what the hell he's been doing, badmouthing Kyojuro, who gave up his life, and then hitting the only son he has left. Shinjuro shouts that he knows Tanjiro is just mocking him because he's a Sun Breathing user who's just full of himself because he can use the original Breathing Style, and Tanjiro shouts back that he can never get full of himself because of how badly he's just been beaten down. Running at Shinjuro, the young Demon Slayer tells him never to speak ill of Kyojuro again.

Senjuro tries to warn him that Shinjuro is a former Hashira, but, because he's being driven by so much anger and sorrow, Tanjiro continues to charge at him. Shinjuro hits Tanjiro's face, ignoring the yells of protest from his son, and begins to repeatedly land blows on Tanjiro's body until the young Demon Slayer hits him square in the jaw with a spiralling headbutt, causing them both to fall down on top of each other.

After Tanjiro leaves, Senjuro returns to the house and finds Shinjuro drinking on the porch. Upon hearing Senjuro's voice, Shinjuro immediately lashes out and shouts for him to leave; however, before Senjuro leaves, he says Kyojuro's last message: "please take care of your body." Shinjuro then puts down his drink and breaks down in tears over Kyojuro.

Infinity Castle Arc
Following Kagaya Ubuyashiki's death and Upper Rank Four Nakime's summoning of the Infinity Castle, Shinjuro is seen sitting in the Butterfly Mansion alongside former Sound Hashira Tengen Uzui. He praises Kiriya Ubuyashiki's ability to command the Demon Slayer Corps even after his father's death, and silently vows to follow Kyojuro's example and risk his life for their protection and to not bring shame to the Rengoku family.

Abilities
Overall Abilities: Due to his status as the former Flame Hashira of the Demon Slayer Corps, it can be assumed that Shinjuro is a very powerful swordsman. In a brief skirmish, he was able to completely overwhelm Tanjiro Kamado, a talented Demon Slayer who was pivotal in the defeat of Enmu, in hand-to-hand combat. He was noted by Tanjiro to not "move like an average person", hinting to his above average physical abilities as a seasoned Demon Slayer. A further testament to Shinjuro's strength is that he was able to defeat the future Lower Rank Two, Hairo, while in a drunken rage.

Breathing Style
Flame Breathing (の): One of the core Breathing Styles, this style ran in the Rengoku family since the invention of Breathing Styles and is passed eventually passed down to his son, Kyojuro.

Trivia

 * Shinjuro's entire first name contains the Go-on'yomi reading for the kanji for "twig, yew plum pine", "longevity" and "son, male".
 * Interestingly, the first kanji of Shinjuro is the traditional Kyūjitai character instead of the simplified character.
 * It is unknown why, but Shinjuro hates animals.

Quotes

 * (In response to Tanjiro Kamado) "A person's capabilities and limitations are set at birth. A rare few enter the world with talent the rest are just rabble! They're dust! Of no value!"
 * (In response to Tengen Uzui) "That's right. The young children are rousing themselves to this degree of action. Like Kyojuro, I will risk my life to protect them, so I will not bring shame upon House Rengoku."

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