Spika (スピカ, Supika) is one of the Four Guardians. She is very quiet and polite, addressing Cross and Ruby as "master" and "young miss". She greets Ruby and Cross kindly and politely asks them to go home, and when they tell her the exit is behind them, she cheerfully tells them that the path behind her leads to hell, scaring the two. As they comically run away as fast as they can, she holds the ring around her neck to her mouth and her personality changes completely as she angrily yells at them to not ignore her. The ring takes sound waves from the air and creates giant letters that can be used for attacking. Certain words have different characteristics, such as the word "spike" creates spiky letters and the word "sticky" creates letters made from a sticky goo. She is fighting Ruby and is nearly caught by two halves of a rock moving towards her, but is accidentally saved by Futomomotaro getting caught between the rocks and becomes Futomomotarou's "wife". She and Futomomotarou often have little 'love scenes', comically scaring the rest of the crew. Spika now fights with the Crew of The Orphan because she is now 'loyal to her husband, not the Zenom'.
Spika's name is probably a pun on the English word "Speaker" which matches her ability to materialize words.