Shinjuro Rengoku

Shinjurou Rengoku is the father of Kyoujurou Rengoku and Senjurou Rengoku and the former husband of Ruka. He formerly served as the Flame Pillar in the Demon Killing Corps.

Appearance
Shinjurou strongly resembles his son, Kyoujurou. Their facial structure, eyebrows, and hair are almost identical.

Shinjurou wears a traditional kimono robe. In the Dimensional Infinity Fortress Arc, he is shown with a katana with a flame guard similar to Kyoujurou's and what appears to be a flame pattern on the sheath.

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

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

He later enters the Dimensional Infinity Fortress alongside the other Demon Hunters and vows to follow Kyoujurou's example and not bring shame to the Rengoku family.

History
Sometime before the Demon Train Arc, Shinjuro tore apart the Generational Flame Pillar Record of the Rengoku family.

Demon Train Arc
Following Kyoujurou's death after his battle against Upper Moon Three Akaza, Tanjirou Kamado visits the Rengoku residence in order to learn more about his Dance of the Fire God, where he mets Shinjurou and Senjurou. Upon hearing about Kyoujurou, Shinjurou immediately begins berating Tanjirou, insulting Kyoujurou in the process, causing Tanjirou to retaliate in anger. Shinjuro then attacks Tanjirou after recognizing Tanjirou's earrings as those of a user of the Breath of the Sun, beating up the injured Tanjirou until he is eventually knocked out by a headbutt.

After Tanjirou leaves, Senjurou returns to the house and finds Shinjurou drinking on the porch. Upon hearing Senjurou's voice, Shinjurou immediately lashes out and shouts for him to leave; however, before Senjurou leaves, he tells Shinjurou Kyoujurou's last message: "Please take care of your body." Shinjurou then puts down his drink and breaks down in tears over Kyoujurou.

Dimensional Infinity Fortress Arc
Following Oyakata's death and Upper Moon Four Nakime's summoning of the Dimensional Infinity Fortress, Shinjurou 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 Kyoujurou'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 Shinjurou is an extremely powerful swordsman. In a brief fight, he was able to completely overwhelm Tanjirou Kamado in hand-to-hand, but was eventually knocked out with a powerful headbutt. He was noted by Tanjirou to not "move like an average person".