A spinoff of Ore no Imouto ga Konnani Kawaii Wake ga Nai following Kuroneko's route. This manga is a new story based on volume 15 and 16 of the Oreimo lightnovel written by the original author Tsukasa Fushimi. Not to be confused with Ore no Kouhai ga Konna ni Kawaii Wake ga Nai, which is a spinoff.
My Little Sister Can't Be This Cute: Kuroneko If is a completed manga by Fushimi Tsukasa, first published in 2021. It blends romance, comedy, drama and slice of life. You can read all 27 available chapters of My Little Sister Can't Be This Cute: Kuroneko If online for free on MangaPulse; the newest is Chapter 27, added 2024-02-18. The series is finished, so you can read it from start to end in one go.