Well... thats was the most erotic wincest that the Rinka's onichan wont remember ever.
Be my guess, i love Rinka works more of the other girls because she had this more mature pervert aura around her than the other... and this wincest manga just prove me right.
Erotic Rinka's body, with a savage libido for her bro that leds her to drug and toy with him in some of the most lewd sex positions just to ensure to take his cum... Glorious!