Both stories certainly don't skimp on the violence with which children can be involved in. Especially given that the start of it all is an encounter with a bizarre and somewhat cute creature who becomes their friend.
While Narutaru goes on the more psychological side of the spectrum and Tomodachi x Monster on the more action one, they both contain:
-Violence on/between children
-Pokèmon like creatures
-A twisted bond within the kids and the creatures