Little Sister

Little Sister (妹, Imotou) is chapter 20 of the Boku wa Tomodachi ga Sukunai light novel series. It is chapter eight of volume two.

Summary
After witnessing her brother prepare lunches for Maria, Kobato expressed displeasure through facial expressions. Meanwhile, on their break, Kodaka delivered his packed lunch to Maria, as Kodaka promised to make her one again the next day, and Maria began addressing Kodaka as "Onii-chan" because of this. During dismissal, after arguing over who Kodaka's true owner is, the latter found Kobato inside the clubroom and came to warn her brother about prioritizing the club over her. At the same time, Maria came into the clubroom after Kodaka promised Kobato to cook her pork ramen on weekends as his act of forgiveness towards her. After seeing Maria as she clung to Kodaka's arm, Kobato immediately separated her from Kodaka out of anger as she flung insults towards Maria. Addressing herself as an ancient vampire, Kobato and Maria began to bicker at each other as Maria proved to Kobato that she is more mature than her by proclaiming her knowledge about sex, which she offers to do with Kodaka, much to the surprise of others. After Rika lectures Maria about sex, Maria, frightened, came clinging to Kodaka's arm as Kodaka held disgust towards Rika. Seeing this, Kobato attempted to separate Maria from her brother before exiting the clubroom.

Later that evening, at the Hasegawa Residence, Kobato declared to her brother that she will be sleeping with him in his room.

Kobato:"...An-chan is my An-chan..."

The next day, after school, as Kodaka heads into the clubroom, he again finds Kobato inside as she proclaimed on joining the Neighbor's Club in order for her to keep a close watch on her brother. While Sena and Yozora both agreed on letting Kobato join, the latter once again came face-to-face with Maria which ensued another fight between them, much to Kodaka's dismay as Sena and Yozora cringed towards Kobato and Maria's quarreling. And the Neighbor's Club has garnered yet another unfortunate member, Kobato Hasegawa.