Guardians 4(ガーディアンズ4,Gādianzu Fō?) was a Hello! Project unit consisting of Aika Mitsui from Morning Musume, Yurina Kumai and Risako Sugaya from Berryz Kobo, and Saki Nakajima from Cute. It was formed for the sake of performing music for the Shugo Chara!anime. Each of the group's singles has been used as an opening theme for either Shugo Chara!! Doki or Shugo Chara! Party, and each single has included a track by Shugo Chara Egg! (who immediately preceded Guardians 4 in singing theme songs for the show). On March 10, 2010, a compilation album and DVD compilation were released featuring songs by Guardians 4, Buono!, and Shugo Chara Egg!, titled Shugo Chara! Song Best and Shugo Chara! Clip Best respectively. The final episode of Shugo Chara! Party aired March 27, 2010, effectively ending the group's activities. It was known that the group leader was Saki Nakajima from the making of PARTY TIME.
Like Shugo Chara Egg!, the four members of this group wear costumes inspired by the anime. In this case, the costumes are based on the school uniform of the Seiyo Academy (a key location in the series), but with the "royal cape" also worn by the "Guardians" (the student council that main character Amu Hinamori "joins"), hence "Guardians 4". Each of the members wear the same color, although that color changes with each single.