It runs in the family, don't worry about it.
Their Grandfather and Father are also in a sexual relationship, Sekai and Mio feels mild in comparison. From what I can tell, Grandpa is an unaging 28 year old in his 70's. I don't know if they needed to consummate, or if there's some supernatural conception of holding hands to birth a child.
Wait what's the name of the manga??
The sauce??
483609
holy shit
sry wrong one, it's 504876
Is the manga name?? Like how to search for it
Maybe you’re better off not knowing lolol. it’s an nhentai code, but you can also find it on bato if that’s more your style titled “The Perfect Family”
wait wtf the author cant just drop a "the older bro leads a satanic cult and that's why he's in an incestuous relationship with his younger brother" bomb and not elaborate