I Regard You as My Junior Brother, and You Regard Me as Your Taoist Companion?

[Straight female senior sister x green tea. Yandering young junior brother] The male protagonist is a severely in love brain who spends all day thinking about how to charm his senior sister. The female protagonist is emotionally slow for some reason, and generally cannot feel the male protagonist's attraction to her. He tried all his strength and means to seduce the senior sister, but found that the senior sister could not understand. Yu Moxuan: "Sister, I love you!" Shen Ruhui: "I know, I love myself very much too." Yu Moxuan, who worked hard to dress up: "Senior sister, look at me." Shen Ruhui was puzzled, "What are you looking at? There's no dirt on your face?" Yu Moxuan felt as if he was showing his charming eyes to a blind man. "Right." Seeing Shen Ruhui turn around again, Yu Moxuan was pleasantly surprised and thought she had seen his little thoughts. "Remember to change your clothes later. It's not easy for you to practice sword wearing. You may trip yourself." Shen Ruhui said seriously. Yu Moxuan is completely out of ideas now. Why is the senior sister just not enlightened?