Ruruna feel not confident in her Gyaru association (Gyaru term used for fashionable young girls). Because Ruruna had never had sex, so she could not participate chatting and telling stories with Gyaru friends who are always talking about sex problems. Finally, Ria offers to Ruruna to have sex with Ria's younger brother, so that Ruruna can have experience about sex and can come to tell stories with other friends about sex.
(Source: Translated and Edited from Nekopoi)
(Source: Translated and Edited from Nekopoi)