Akuyaku Reijou no Naka no Hito ~Danzai sareta Tenseisha no Tame Usotsuki Heroine ni Fukushuu Itashimasu~ - Vol. 6 Ch. 26 - Ye Abandon All Hope

[glitches16]

was the brother incest(?) part ever hinted before?
I can't remember that.
Might need to reread this later

They're cousins from what I remember (Whether or not their blood is thick or thin, I wouldn't know). But, if he had been there to support Emi that day, Emi wouldn't have disappeared