Tanjiro Kamado and Inosuke Hashibira vs Spider Demon (Father)

Tanjiro Kamado and Inosuke Hashibira vs Spider Demon (Father) was a battle that took place on Mount Natagumo. It focuses on the battle between Demon Slayers Tanjiro Kamado and Inosuke Hashibira against Father of the Spider Family.

Prologue
After successfully killing Mother of the Spider Family and preventing new puppets from forming, Tanjiro and Inosuke ventured deeper into the forest of Mount Natagumo. Tanjiro then faintly hears the sound of thunder and is perplexed as he does not smell nor see any thunderclouds anywhere in the sky, leading to him questioning why he heard the sound. Inosuke, annoyed at him for wanting to treat/aid him, answers he has no idea or cares. As the latter attempts to cross a river, Tanjiro asks him if he is descending down the mountain. This infuriates Inosuke even more, denying that he is descending because he is injured, despite Tanjiro seeing his obvious injuries. They then witness an pale-skinned girl on the other side of the stream, with Tanjiro and Inosuke immediately recognizing her as a demon, even while Tanjiro couldn't pick up her scent due to the pungent odor all over the mountain. Inosuke immediately engages the girl and chases after her. She immediately calls out to "Father", confusing him. Emerging from the trees, an enormous demon appears and attempts to punch Inosuke, who narrowly misses getting killed. Father yells at the Demon Slayers, "Don't come near my family, stay away!"

Battle
When Father attempts to punch Inosuke again, Tanjiro blocks his arm with his Water Breathing, Second Form: Water Wheel. The cut is too shallow to do damage, leaving Tanjiro stuck in his thick skin. The demon tries to hit him with his free arm but is stopped by Inosuke, who also struggles to slice through. Father breaks free and tries to attack a nearby Tanjiro; Inosuke leaps towards him from behind but Father hears his approach and punches him away.

Inosuke is pursued in the shallow river, forcing Tanjiro to intervene; using Water Breathing, Second Form: Improved, Lateral Water Wheel, he slices a nearby tree and causes it to fall atop the giant demon, pinning him and saving Inosuke. Seeing the demon trapped underneath, Tanjiro opts to kill Father using his final and most powerful form. Leaping into the air and preparing to use the Tenth Form, Father pushes upwards and uses the fallen tree to catch Tanjiro mid-air.

With his blade firmly stuck in the trunk, Tanjiro watches helplessly as Father hurls him away, launching him a great distance into the forest. Seeing his friend in peril, Inosuke calls out to "Kentaro"; Tanjiro warns him about Father being a Twelve Kizuki and begs him to stay alive as he hurtles away. Now alone, Inosuke watches as Father approaches him for the kill. Inosuke runs into the forest in an attempt to escape Father, as he struggles to find a way to beat him despite his incredible durability. The demon spots him and attacks, destroying the tree he was hiding behind. The Demon Slayer runs away but suddenly stops in his tracks; unable to believe he is retreating from a battle, he heads back and decides to face Father head on. He jumps up and slams his blade home, cutting into Father's forearm.

Cursing that his mentality is becoming like Tanjiro's, Inosuke repeatedly hammers his sword and succeeds in cutting off the demon's arm. At the sight of his amputation, the demon runs away and Inosuke gives chase. He spends time running through the forest in search of Father, stopping on occasion to soak up the pain of his injuries but pushing on. With great difficulty, he uses his acute sense of touch and locates Father hiding up a tree. Believing the demon is hiding at the sight of him, he proves to be mistaken when the Spider Demon's body begins to abruptly change, shedding his old skin and revealing a new form. Seeing he is overwhelmed by the more powerful demon, Inosuke pauses and believes it is pointless to fight. Suddenly remembering Tanjiro's words to stay alive, as well as Hisa's advice to live with pride, he declares he is a member of the Demon Slayer Corps and tells him to, "Just bring it on, you dirtbag!".

His sudden confidence is silenced when Father strikes him square in the body, causing him to slam into several trees before stopping. No soon after he lands, the demon appears and tries to crush him with a punch. Inosuke dodges in time and jumps up, breathing for an attack as he descends. Using his Beast Breathing, Third Fang: Devour, he swings both swords at Father's neck but the blades break upon making contact. Unharmed, Father turns around and slams him into a tree. Too injured to move, Inosuke is grabbed by the head by the demon and slowly crushed. He makes a desperate attempt to hurt Father with Beast Breathing, First Fang: Pierce but the giant demon doesn't flinch when his broken swords stab him. Slowly dying as he is crushed, Inosuke reminisces on his life, suddenly seeing a woman apologizing to him. He wonders who she is as blood pours from his mask.

Intervention by a Hashira
Speeding into the forest in the nick of time, the Water Hashira, Giyu Tomioka, sees the demon and easily slices off his arm, freeing Inosuke from his hold. Inosuke lands hard on the ground but sees someone has rescued him; Giyu commends him for surviving this long. Enraged, Father attempts to kill Giyu and charges at him. Undaunted, Giyu retaliates with Water Breathing, Fourth Form: Striking Tide, slicing the giant demon to pieces with ease.

Amazed at Giyu's skill, Inosuke immediately challenges him to a find, to Giyu's bewilderment. Believing if he can beat him, he can be the strongest, Inosuke is quickly shut down by the Hashira telling him to keep training. Inosuke challenges his opinion, mentioning that he's killed a Twelve Kizuki; Giyu denies this and claim Father was nothing close, while unwinding some rope. With incredible speed, he ties Inosuke up and leaves him hanging on a tree, causing Inosuke to yell at him to return and eventually losing consciousness. He would soon be found by the Kakushi and taken to the Butterfly Mansion with severe injuries.