Shugo Chara! Vol 8

From the Kodansha edition

WITH A LITTLE HELP FROM THEIR FRIENDS Ikuto has disappeared, and it’s up to Amu and her fellow Guardians to save him. But what about Tadase’s mysterious past with Ikuto? And what does that mean for Amu and Tadase’s relationship? Plus, Rima learns the truth about Nagihiko’s double life! This volume of Shugo Chara! includes special extras after the story!

Source: Anime News Network Encyclopedia