|Created by||Akira Jotaro (aka Justice0)|
|No. of episodes||28|
|Run time||22-25 minutes|
The story is set in modern Japan in a fictional city called Tsuto, where weird things often happen. The story is about a high school student who wishes to live his life normally but had his life drastically changed when he met a strange girl.
Len Tsubame is a lazy and unmotivated person who has average grades, a few friends, and a hobby of playing video games. One day, his little sister had died of illness and the day after the funeral, on the way home from school, Len is attacked by a girl trying to rob him, but failed to steal it. After he left, he heard her crying and told her to follow him if she wanted, which she did. Once they were at his home, Len had met the ghost of his little sister when he was looking for something to serve the girl, and after a few minutes, a strange monster attacks his apartment and the girl transformed and fought against the monster. After the monster was killed, Len's life was changed drastically, he later met a witch, an idol, his childhood friend, a wierd senior, a kung-fu girl, and a transforming cat, creating what his friends call "History's Weirdest Harem".
- A lazy and unmotivated student of Tsutomu High School. He had once wanted an anime-like life when he was younger but as he grew up, he had only wanted a peaceful and normal life. Even though he doesn't want it, he has attracted a weird bunch of girls who loves him and is constantly annoyed by it. He often breaks the fourth wall and talks with the narrator when things doesn't make sense, he also sometimes complains of how the title doesn't fit the show. He is voiced by Atsushi Abe.
- A man who often makes jokes and sarcastic remarks about the anime. At the beginning, he actually told the story as if nobody noticed him and did not make any jokes. He was named Ichigo after the second narrator had made his debut. He is voiced by Fumihiko Tachiki.
- Len's deceased adopted little sister and a ghost who refuses to pass on. She has a major brother complex with Len and often gets jealous when he is with another girl. She is nice to people but is really mean to people who really like Len or are mean to him. She is bounded to Len's apartment and cannot leave it. She is voiced by Hisayo Mochizuki.
- A girl who had tried to rob Len in the beginning because she had lost all of her money during her travel to Tsuto. She is actually a magical girl who is looking for monsters known as Corruptors to defeat them and save the world. She is a kind and childish girl the same age as Len. She lives with Len. She is voiced by Fumiko Orikasa.
- A gothic and dark but very smart girl a year younger than Len but in the same grade. She is often seen as emotionless and evil girl due to her dark aura of being a witch. She is the newest transfer student to Tsutomu High School and Len was the only student in the entire school who wasn't afraid of her at the time. She sometimes stalks Len but was caught by the narrator many times. She is voiced by Mamiko Noto.
- The most popular pop idol of Japan. She is a girl who likes to act high and mighty but is very scared of ghosts. She had transferred to Tsutomu High School due to a stalker problem she had in Tokyo. She, like Len, often complains to the narrator when things doesn't make sense. She is voiced by Maaya Sakamoto.
- The childhood friend of Len and a girl obsessed with kendo. She was in Len's kendo class when they were 7 years-old until Len quit when he was 11. Even though she had went to the same school as Len, they had not noticed each other until she bursted into Len's class while chasing a stray cat that stole her underwear. She is the only one of the characters who doesn't notice the narrator or know that they're in an anime. She is nicknamed Ina by Len. She is voiced by Arise Satō.
- A senior in Tsutomu High School who often flirts with girls but had fallen in love with Len after he accidentally saved him from being hit by a truck. He still flirts with girls but often jumps towards Len to hug him and usually ends up on the ground from being punched or kicked by him or one of the girls. He is voiced by Takuma Terashima.
- A Chinese transfer student of Tsutomu High School who enjoys martial arts and cooking Chinese food. She is an easy-going girl who loves animals and usually hugs them whenever she sees an animal. She is a master of the bajiquan style and also knows the zui quan style due to the fact that she gets drunk very easily; even a strong scent of alcohol can get her drunk. She believes that the narrator is some kind of deity and is scared of getting him angry. She is voiced by Li-Mei Chiang.
- A cat that has the ability to transform into a human. She was a stray cat that was picked up by Len in the rain one night after he was coming home late. She treats Len as her master and would do anything he tells her to do. She is voiced by Yui Horie.
- One of Len's friends. A student of Tsutomu High School who wishes to have the life of a boy with a harem full of cute and beautiful girls. He often breaks the fourth wall complaining to the anime director and producers on why he couldn't have his own harem anime. He is voiced by Daisuke Ono.
- Len's best friend. A student of Tsutomu High School who doesn't talk much. He has been best friends with Len since middle school when he was saved from being beaten up by bullies. He knows about them being in an anime and the narrator but chooses not to notice it but sometimes wonders why he's named after a famous swordsmith. He is nicknamed Masune by his friends for short. He is voiced by Jun Fukuyama.
- Her name is a pun for "suspicious person" in Japanese. She is a cute but very shy girl who has a crush on Masamune and went to Len for help, making Toshie mistaking her for being part of Len's harem. Before she confessed to Masamune, she was stalking him and often gives him good luck. She is kind and innocent so she didn't understand what the narrator was talking about when he makes sexual jokes about her chest. She is voiced by Chiaki Omigawa.
- The second narrator of the anime. He is the substitute for the original narrator for a few episodes. Like the original narrator, he often makes jokes about the anime and characters but cares less about what goes on. He sometimes argues with the original narrator when they are together. He was named Nigo after he had his first debut with the first narrator. He is voiced by Norio Wakamoto.