[Rocomani (Manatsu Roco)] Sonohi Konyakusha no Imouto to Boku wa | On That Day Together With My Fiance's Little Sister [English] {Doujins.com} [Digital]
When the saying "Don't stick your dick in crazy" fails to account for psychotic extreme-siscon imouto-in-laws forcibly mounting MCs out of nowhere after meeting for literally the first time.