After Erika lied about having a boyfriend, Kyouya helped her out by becoming her fake boyfriend, in return Erika had to be Kyouya's dog. After a while of pretend dating, Erika finds herself falling for Kyouya and it was hinted Kyouya planned to fall in love with Erika if he hadn't already. At the beginning the pair have a rocky relationship with Erika being bossed around by Kyouya as his dog, their relationship has its ups and downs as the pair often argue with Erika's feelings being at the base of the arguement but Kyouya soon makes it up to her somehow. Eventually Kyouya and Erika become an official couple as Kyouya tells Erika his feelings. She deeply cares for Kyouya a lot and does get annoyed when other girls approach him. In Chapter 25 Erika's cousin Rena falls for Kyouya and she felt uneasy about it but she felt happiness when Kyouya stated he wasnt interested in Rena and he would get bored before she even becomes his girlfriend although she felt sorry for Rena. At the end of the manga the two of them get married and had a daughter.
Yuu fell in love with Erika because she was kind to him. Erika gave him valentines day chocolate which made Kyouya jealous. He then told Kyouya that he liked Erika and is going to confess to her. Erika and Yuu's relationship didnt work out because Erika loved Kyouya more. In Chapter 23 he gets a Girlfriend.
Kimura was Erika's 'first love', she fell in love with him when he stuck up for her against a few off Kyouya's fan girls who were bullying Erika for being Kyouya's fake girlfriend. The two even went on a date before it was revealled Kimura only wanted to date her because she was Kyouya's girlfriend, he held a grudge against Kyouya after Kimura's girlfriend broke up with him because she'd fallen in love with Kyouya.
Ayumi is Erika's best friend and is the only true friend who knows about Kyouya and Erika's fake relationship. She often calls Erika a masochist or a narcist for putting up with Kyouya and allowing him to treat her like his dog. Ayumi often helps out Erika and gives her advice on her relationship with Kyouya, she even said she enjoys seeing the pair interact with each other and finds it interesting/amusing.
Takeru is a good friend to Erika he helps Erika and Kyouya get together by finding out what Kyouya dislikes and likes all of Takeru's Ideas didnt work because Kyouya knew what was happening. Takeru was happy to know that Kyouya and Erika became an official couple.