Nadeshiko Fujisaki (藤咲なでしこ, Fujisaki Nadeshiko) is the female alter ego of Nagihiko Fujisaki. She's the minor character of Shugo Chara and the former Queen's Chair of the Guardians.
Nadeshiko is the former Queen's Chair of the Guardians. When Amu rejected the offer to join the Guardians, Nadeshiko tried several tactics to convince Amu to join. The two eventually become best friends and Nadeshiko looks over and supports Amu in her love life. When Amu went to Nadeshiko's house for a sleepover, she also stated that Nadeshiko was really pretty, and that she could dance really well.
The reason that Nagihiko has a female ego is because in the Fujisaki family, boys must cross dress as girls in order for them to learn how to dance. Amu has seen Nadeshiko dance for practice, but has only seen her real performance once in the anime. As Nadeshiko, "she" can pull off as a girl because Nadeshiko had been in the disguise for a long period of time. Tadase, Kukai, Rima and their Guardian Characters are the only people who know Nadeshiko's gender secret. He has skipped gym and swimming class, as said in Chapter 8 of the manga, so that his/her identity is more easily protected because of the swimsuit.