Ninja Kids!!! Summer Mission Impossible (2013)

Original title: 忍たま乱太郎　夏休み宿題大作戦！の段

At a time when nations are warring, a sword with mysterious power called "Heaven's Sword" is stolen. The sword is said to give its wielder the power to conquer the world. Various ninja all over Dokutake Castle and beyond also manuevering for this sword of immense power. Rantaro and his classmates are assigned to retrieve the stolen sword, their first real ninja mission.