Shinjuro Rengoku (
Shinjuro strongly resembles his son, Kyojuro 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 angry, 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. In the Dimensional Infinity Fortress 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.
Shinjuro is a very short-tempered man, especially when regarding the Demon Slaying 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.
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 enters the Dimensional Infinity Fortress alongside the other Demon Slayers and vows to follow Kyojuro's example and not bring shame to the Rengoku family.
Sometime before the Demon Train Arc, Shinjuro tore apart the Generational Flame Pillar Record of the Rengoku family.
In Kyojuro's Blood Demon Technique-induced dream aboard the Demon 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 Pillar 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 Moon One of the Twelve Demon Moons, and Akaza, Upper Moon 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 Breath of the Sun 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 Breath of the Sun user who's just full of himself because he can use the original Breath 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 Pillar, 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.
Following Oyakata's death and Upper Moon Four Nakime's summoning of the Dimensional Infinity Fortress, Shinjuro is seen sitting in the fortress, ready to fight, alongside former Sound Pillar Tengen Uzui. He praises Kiriya Ubuyashiki's ability to command the Demon Slaying Corps even after his father's death, and silently vows to follow Kyojuro's example and risk his life for their protection and not bring shame to the Rengoku family.
Abilities and Powers
Due to his status as the former Flame Pillar of the Demon Slaying Corps, it can be assumed that Shinjuro is an extremely powerful swordsman. In a brief fight, he was able to completely overwhelm Tanjiro in hand-to-hand, but was eventually knocked out with a powerful headbutt. He was noted by Tanjiro to not "move like an average person."