My Friend's Little Sister Has It in for Me!

I'm not interested in forming deep emotional connections or finding a girlfriend. My priority is having a single friend who is valuable to me. To maximize my time, I only allow one person in my bedroom - Iroha Kohinata, my friend's bothersome and sometimes irritating younger sister. Despite her reliance on energy drinks and constant attempts to seduce me, Iroha continues to pursue me even though I'm busy with other things. It's no wonder others are envious of her, as she's recognized for her outstanding academic achievements and kindness in school. However, I can't help but wonder why she becomes unbearable when spending time with me.