It's rough to transmigrate, and even rougher to transmigrate into your own self from two years ago in a parallel world.
Kirigaya Suguha expressionlessly raised her middle finger to the sky and shouted in her heart: Fuck you! The two worlds are almost exactly the same, so why did those damn gods of Takamagahara turn my all-conquering top of a cousin into this adorable otaku bottom? This makes no sense! It'd be one thing if my brother in this world had become a bottom, but he actually got involved with a Mary Sue! That's way too damn cruel. Give me back my BOSS sister-in-law! (You know what Takamagahara is: the place where Japan's eight million gods live, the heavenly realm of Shinto.)
This is the story of a fujoshi cousin from a parallel world who tries to turn her cousin into a top, punches the Mary Sue, kicks the clingy little sister, protects her brother's virtue, and helps him pursue his "sister-in-law," only to be treated by said "sister-in-law" as a promising little fruit to be thoroughly toyed with.
Bottom brother: The Mary Sue and the clingy little sister are so scary! (>_