After a period of time post the events of Hozuki-san Chi no Aneki, (+Imouto) dives back into the mischievous world of Gorou, a perverted sister-complex enthusiast, and his older stepsister, Haru. But when Haru's cousin pays a visit, Gorou's unwavering adoration for Haru is put to the test, leaving her feeling the absence of his once boundless attention.