Little D. No 2 is a tiny demon helper at the Demon Lord's Castle and is mentioned to have assisted MC with the assigned RAD tasks. It is first introduced in the story in Lesson 7-10.
In Tasks, it appears as a battle opponent with Special Skill "SHADOW ATTACK" spelled in reverse.
Its battle dialogue also includes "CHAAARGE" and "NnnNnEEeeXttTT" spelt in reverse, and "coup DE Grace" in reverse word order with the "DE" spelt in reverse as well.