Family reunion

After the events of the graduation, the four headed to headquarters, where they would coordinate and prepare to dispatch to the Spider Kizuki. Frankly, it was a mission Giyu could have handled on his own, but Banjiro knew it would be a great learning experience, so he gathered the Hashiras and Demon Slayer Corps against the Spider Family, using the Hashira to teach the Demon Slayers how to handle unique situations and a Kizuki. There was no chance of getting away; they made sure to keep the place tight, allowing Banjiro, Zenitsu, Nezuko, and Inosuke to get along as they fought against Rui. In this mission, Banjiro also met with his other family members, mainly Hanako, who had grown into a beautiful young woman with an admittedly slutty lifestyle, even amongst her brothers. Still, she had a big pair of tits, a thin waist, and nice thighs, so she was still VERY attractive in Banjiro's eyes, making their family reunion hug zesty as his big dick pressed against her stomach, eliciting a cheeky response from Hanako.

"Are you training, or are you just happy to see me?" Hanako said as she did a mini jump up, laying her cunt against the tip of his erect dick, pressing so hard down that it slightly entered her pussy, causing her to orgasm on the spot and tighten her muscles as she slammed into his face for a French kiss. Ultimately, Nezuko had to be the one to separate them as their other siblings caught up, looking at Nezuko as she held them both by their collars, chuckling and asking if Hanako tried to seduce Banjiro again.

The group then headed back to the Demon Slayer headquarters, where Banjiro's special contact had finally arrived and where Banjiro's friends were healing. It was there that he introduced Nikola Tesla, using him to upgrade Inosuke's blades into chainsaw katanas while helping Shinobu implement a Demon Slayer Corp poison gun and special coating mechanism that would release liquids poisonous to Demons on the blades. He was also there to help create new concoctions, but the engineering sciences were closer to his expertise, so they had him do that, as Tamayo also assisted/was aided by the other two in creating a cure.

Also, he had Shinazugawa's brother, his experimental Demon-eating, and a shotgun, also added to the Demon Slayer arsenal.

This gave a bit of time before the train arc, allowing Banjiro to continue learning from the other Hashiras on diversifying his sword style as he worked to create what he called World Breathing, a united form of all the breathing styles that elevated and united the Sun Breathing with elemental breathing. In the meantime, he could also get closer to Mitsuri and Hanako, who were already in the bag and, pleasantly, in a master-disciple relationship as they both used Love Breathing, although Hanako also learned a bit of Sun Breathing. Thus, with his previous grooming, all it took was Banjiro unbuckling his pants in a secluded space with them as he proclaimed for them to be his.

Filled with such love, Hanako was easily swooned, but Mitsuri was a little harder, requiring Banjiro to go into all her lovely details about her strength, body, and personality that made him fall head over heels for her, asking for her to join his harem. In response, Mitsuri agreed on the spot, giving Banjiro a deep-throat she simply couldn't take, underestimating Hanako's slut training as she came and gagged repeatedly, adjusting quickly by keeping herself deep around his meat shaft, her body quivering, becoming an easy target for Hanako to pressure with her mouth.

The noises were so loud that others couldn't help but peep, including Inosuke's, whose primal nature already made her feel something special around Banjiro. However, as Inosuke looked on, that primal urge grew as she found Banjiro to be more and more of a potential mate. Soon, she was finger-banging herself outside, alongside Iguro and Zenitsu, who were shamefully masturbating out of a feeling of cuckoldry. They wept as they saw Banjiro having his way with these three women, twerking their pin-dicks while Inosuke let her moans out like a mating call, not caring for the other two who resigned themselves to silent watchers, only to be discovered.

In this situation, everyone thought they should have a moment to stop and talk, but as Banjiro saw Inosuke's beautiful face, what was about to be a serious conversation turned into a primal fucking that echoed even louder as the two fought for dominance using their private parts, with Banjiro winning because of his girth and experience. Everyone else was either masturbating or engaging in some sort of sexual activity. For the guys, they weren't having sex, but they were getting handjobs or footjobs because of Nezuko's lead to help Mitsuri and Obanai, with Hanako even offering boobjobs and a few kisses on their cocks, but abstaining from any real sex as she was now Banjiro's third wife. Meanwhile, Zenitsu was practically getting **** with how far Nezuko tested her limits and how far she could push him into being her little bitch, awakening some sort of hidden desires and fetishes in her that turned her into something sexually dominant and scary.

By the time Inosuke was worn out, and Banjiro finally regained his sense of the situation, both the guys were pathetically sprawled out on the ground as the girls giggled or started enjoying the female touch upon their bodies. It was then that Banjiro had a serious think about what to do. He didn't want to give up his women or share them with the guys, but he also didn't want to ruin their relationships, as would be developed in canon, so he decided to keep them as the girls' cucks for the meantime, while he pondered what to do next, unaware that Shinobu was watching on curiously.