Kage Kara Mamoru! (陰からマモル) is a Japanese series of light novels written by Achi Taro. The light novels had ended in March 2008 with the release of Volume 12, but as of July 2009, a new series entitled Motto! Kage Kara Mamoru! (もっと!陰からマモル!) has started serialization. It features manga and anime adaptations. The main character is Mamoru Kagemori, a ninja who is sworn to protect his neighbor Yūna Konnyaku.
Story
The Kagemori family has secretly protected its neighbor, the Konnyaku family, for 400 years. Mamoru has been the protector of the daughter, Yūna Konnyaku, since they were in kindergarten. When Yūna is in trouble, Mamoru quickly puts on his ninja suit and transforms into a competent ninja; able to protect her from harm. Unfortunately, this poses quite a challenge as Yūna, being both clumsy and absent-minded, often stumbles into situations where Mamoru must once again come to her rescue.
On the first day of their new school term, a model airplane accidentally makes a dive towards Yuna, but it is quickly stopped by a thrown kunai. At school, Airi Sawagashi invites Yūna to go bowling, but is unhappy when Mamoru also comes.
At the bowling alley, Yūna wanders into the men's restroom and interrupts a yakuza deal involving fake dolls. As a result, they kidnap her and take her to their boss. Mamoru follows them, takes out the gang, and rescues Yūna.
The story continues as new characters enter Yūna and Mamoru's lives with both good and evil intentions, wacky adventures, hints of romance, and confrontations with the strangest of adversaries.