Futakoi Alternative is a very loosely done Spin-Off of the original Futakoi, which uses the original character designs and concept of twins and virtually nothing else. The male protagonist is Futaba Rentarou, a 21-year-old Private Detective who spends most of his time waiting for a case. He's accompanied by his twin assistants 15-year-old Shirogane Sara and Shirogane Sojyu, whose mutual affection for him is completely open to a threesome.

Sojyu, Rentarou, and Sara enjoying some croquette in a freshly leveled boxing arena.

Genre Shift occurs almost by the episode throughout this show. One more serious example takes Rentarou from trying to resolve conflicted feelings of romance and responsibility to racing a bio-hybrid squid down a highway on a friend's bike in two adjacent episodes. The show does have an overarching plot, dealing with a mutual (and surprisingly non-rival) sibling love triangle.

Tropes used in Futakoi Alternative include: