Demon Slayer: With Vergil's Template, I'm Muzan's New Daddy

(Only just got a rating after 280,000 characters...)

[Anime Crossover • No Female Lead] [Overpowered] [Seriously Unhinged] [V Breathing!]

[Ding! Congratulations, host! You have bound the Supreme Swordsmanship System!]
[New transmigrator bonus! Vergil Template awarded to the host!]

Transmigrated into the Demon Slayer world as the eldest son of the Kirishima family? Dongfang Qiubai looks at his seventy-year-old father and the mother who gave birth to him at sixty, then falls silent.

His birth not only sends the Kirishima patriarch-whose family line was on the verge of dying out-into ecstasy, but also utterly crushes the branch family's plot to force him out.

Yet no one knows that the Kirishima family's "heaven-sent savior" has already bound the ultimate swordsmanship system and possesses Vergil's template.

For over a decade, he uses his "serious illness" as an excuse, quietly completing the system's cringeworthy edgelord missions beneath everyone's sympathetic gazes.

At fifteen, clad in a long coat with Yamato in hand, Dongfang Qiubai has already perfected his swordsmanship. Hashira level? Nothing special.

Just as he's itching to join the Demon Slayer Corps and show the world what he can do-

His father, now in his seventies and leaning on a cane, threatens to die rather than let him go: "My son! The family estate comes first! You are not going off to that place full of bloodshed!"

Dongfang Qiubai: "..."

On one side, the call to slay demons. On the other, the burden of keeping his family line alive. Armed with Vergil's template, Dongfang Bubai declares: "Only kids have to choose! I'll take it all!"