Kage Kara Mamoru!

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.

Mamoru Kagemori (陰守 マモル, Kagemori Mamoru)

Voiced by: Atsushi Kisaichi (Japanese)

Mamoru Kagemori is a plain boy with disheveled hair and thick glasses, which are actually a disguise. He is the son of a ninja family which has been protecting the Konnyaku family for 400 years. He reveals his true self (without glasses) when he transforms into a ninja to protect Yūna from harm and is very lazy except when he's saving Yūna. He has been friends with Yūna since they were children, and has also been in the same class as her since kindergarten. He has a fear of bears, which developed when he tried to protect Yamame from a bear when they were children. His name: Mamoru, means protect in Japanese.

Yūna Konnyaku (紺若 ゆうな, Konnyaku Yūna)

Voiced by: Mai Nakahara (Japanese)

Yūna is Mamoru's childhood friend and neighbor. She is a quite clumsy and often ditzy girl. These qualities get her into many troublesome situations. Since she has known Mamoru since kindergarten, Mamoru knows everything about her, except for the object that Yūna looks at every night before bed - a photo of herself and Mamoru which she cherishes. It is hinted that she is in love with Mamoru, but is afraid to admit her love to him. She is shown to be jealous of Mamoru interacting with other girls as seen when she prevented Sawagashi and Tsubaki from holding his hands as they slept at the zoo.

Airi Sawagashi (沢菓 愛里, Sawagashi Airi)

Voiced by: Ryōko Shintani (Japanese)

Airi, a wealthy girl, is a classmate and friend of Mamoru and Yūna. She discourages any relationship between Yūna and Mamoru, because, according to her, childhood friends who become lovers are generally unsuccessful. However, this may be a ploy since she has feelings for Kagemori, whom she derisively calls 'Ahoru' ("Mamoron"). She occasionally gives Mamoru hints that she likes him, which he is oblivious to, and she vents her frustration by hitting Mamoru.

Tsubaki Mapputatsu (真双津 椿, Mapputatsu Tsubaki)

Voiced by: Sachiko Kojima (Japanese)

Tsubaki is a miko swordswoman. Her sword can cut anything but nata de coco. She was hired by the yakuza boss in order avenge his earlier defeat at Mamoru's hands. After finding out the truth about the yakuza boss and realizing she had been tricked, she exacts her revenge on him. She also decides to enter Mamoru's school to become more worldly. After Mamoru cheers her up when she was depressed about being old-fashioned, she develops feelings for him.

Yamame Hattori (服部 山芽, Hattori Yamame)

Voiced by: Ai Shimizu (Japanese)

Yamame is a ninja and a relative of Mamoru. She remembers Mamoru comforting her when she was little and is quite disappointed after seeing the glasses-wearing person he has become. When Mamoru saves her from Chin Panji, a Chinese master of Animal Style combat hired by the yakuza boss, she realizes that he hasn't really changed. The next day, Yamame transfers to his school. She is also responsible for Mamoru's fear of bears (he had protected her from a wild bear, but was attacked and injured by it).

Hotaru Kumogakure (雲隠 ホタル, Kumogakure Hotaru)

Voiced by: Erina Furukawa (Japanese)

Hotaru is a ninja. She confesses her love to Mamoru when they first meet. She and her brother are scheming to defeat Mamoru (a member of the strongest ninja clan) in order to avenge their clan's disgrace in losing to Yamame at a ninja athletic meet. Her feelings for him prevent her from finishing off the wounded Mamoru and she instead administers some of her family's secret medicine mouth-to-mouth thus allowing him to defeat her brother. Afterwards, she moves into the neighborhood and starts attending the same school.

Bluemaru (ぶる丸, Burumaru)

Kagemori family's bull terrier ninja dog. Despite his cute appearance and lazy nature, Bluemaru is actually a very skilled canine and is able to use various ninja weapons in his mouth.

Sakurako Kagemori (陰守 桜子, Kagemori Sakurako)

Sakurako is Mamoru's mother. She is a ninja and is in charge of protecting Yūna's mother.

Kengo Kagemori (陰守 堅護, Kagemori Kengo)

Kengo is Mamoru's father. He is a ninja and is in charge of protecting Yūna's father.

Miminosuke (耳の介, Miminosuke)

Yamame's ninja rabbit companion.

• Kage Kara Mamoru! (anime) at Anime News Network's encyclopedia
• Kage Kara Mamoru at Aniplex (in Japanese)