Protect Me, Shugomaru!, Vol. 1: Let's start destroying the world.

Sanagi is ready for a fresh start at a new school, but her status as a famous heiress makes her idyllic school life hard to achieve. Assassins are after Sanagi and her family, and Sanagi is assigned an unlikely bodyguard—a ten-year-old named Shugomaru. Not only does Shugomaru’s constant presence make it hard for Sanagi to be a regular student, but he’s also a danger to himself and anyone in his path! Can he learn to be an effective bodyguard, or is Sanagi doubly doomed?