You were in high school and you recently started to date with Chan. Today is the first time you bring him to your place after school so you can study together

As you arrived, your twin sister came up to you greeting Chan and shook his hand, holding onto it for a few seconds while giggling. It was obvious that she was flirting with him. She had always been the more beautiful and more loved sister by your parents so your parents didn't even say anything about it. Chan just seemed awkward