Ore no Imouto ga Saikou no Okazu Datta: Cool na Kanojo ga H no Toki Dake Dereru Riyuu

"Looks like my brother — is a big pervert."
When my own sister sees me masturbating to a pornographic incest game, she decides help me out. For some reason, she uses her mouth. My own sister! Our play becomes more and more intense, even though my sister is always scolding my lustful desires, From teasing to loli-cosplay to blowjobs to unprotected ejaculation! Is my sister really going to cure me of my sexual perversions?
(Source: France Shoin, translated)