My Relationship Development Situation with My Friend's Angelic Younger Sister

My favorite streamer was confiding their interpersonal troubles on social media. While wanting to help, I myself don't actively engage with others much, and unable to offer any suggestions, I was invited by my friend Masai to go play at her house. Masai has a cute younger sister named Miai, but normally she stays in her room and runs away when I try to talk to her. Despite wanting to get along with her—which would be rare—things never worked out, and I was getting fed up with the situation. However, whether it was due to some accident that happened today or some other factor, Miai started reaching out to me, which was different from her usual behavior. Moreover, her voice sounded... familiar? This is a story about how the friendship deepens a little between my friend's younger sister and the main character girl who had been wanting to get along with her. *This work is also posted on "Kakuyomu" and "Pixiv."