Tomodachi no Imouto ga Ore ni dake Uzai

Akiteru Ooboshi lives by one rule: do not waste time on anything useless. He pours his energy into the small game-development team he runs with his friends, especially after their latest title becomes an unexpected success. To secure support from a major company owned by his uncle, Akiteru accepts a strange condition that still seems efficient enough: pretend to be the boyfriend of his cousin Mashiro.

His life already contains one major source of inefficiency. Iroha, his best friend’s younger sister, constantly invades his room, teases him, and goes out of her way to annoy him in ways she never does with anyone else. Once Mashiro enters the arrangement, the line between a fake relationship and genuine feelings begins to blur. Akiteru, who considers romance a waste of time, discovers that emotions are the one problem his obsession with efficiency cannot neatly solve.