Simple Mindedness, Innocent, Simple Minded, Naive
Noun and な adjective
むじゃき
子供達は無邪気に笑い合っていた。
The children laughed innocently.
If there is nothing wicked about your spirit at all, you are a going to be an innocent and simple minded person.
This is a jukugo word that uses the on'yomi readings of the kanji. You should be able to read this on your own.