Manaka is Masaki's elementary-school-aged younger sister. She's a devious girl who first started having him dress up as a cute girll to impress Sumika and then sent pictures of him to a modeling agency that ended up hiring him. Despite her awareness of Sumika's feelings for Ushio, she fails to understand why Sumika rejected him and is angry with her for doing so, even going as far as to blackmail her to go on a date with Masaki. She doesn't take into much consideration Sumika's feelings or well-being nor her brother's embarassment, and her intentions motivating some of her schemes involving him are questionable...