Shugo Chara! Vol 9

From the Kodansha edition

A BIG DISCOVERY Amu and the Guardians are battling the Easter Corporation in order to save Ikuto. But during the fight, two surprising things happen: Ikuto’s troubled past is revealed, and the powerful Embryo appears! Who will catch the egg that makes dreams come true? This volume of Shugo Chara! includes special extras after the story!

Source: Anime News Network Encyclopedia