The third term has begun, and a new homeroom teacher has been appointed to class 5 and 3 at Takehaya Elementary School. His name is Toshihiko Ochiai. When Hiroshi and his five friends saw his face, they were shocked. It turns out that Ochiai is the suspicious man who was following Hiroshi's activities and taking notes yesterday. However, it was also true that Ochiai had a mysterious charm that set him apart from other teachers.

The monster Matenro, who was supposed to be a fictitious entity, actually appears and steals Hiroshi's precious computer. Matenro challenges Hiroshi to win in a battle of wits against him if he wants his computer back. Yasuko couldn't believe what Hiroshi was saying, but she too encountered Matenro, who appeared dashingly in a car of light.

Hiroshi and the five of them form the detective team "Hadogumi" to take on Matenro's challenge. However, as they are elementary school students, they are busy with homework and other things, so it seems difficult to concentrate on their activities as Hadogumi. Just as they are already facing these worries, Ochiai-sensei comes and invites the five to play hide-and-seek. The five people hid under a manhole, but...

Hiroshi and his friends suspect that Matenro's true identity is Ochiai Sensei, and begin investigating Ochiai's background. However, Ochiai is a completely dull man, and even if I'm mistaken, he doesn't seem to be Matenro. Matenro appears in front of the Hadogumi, who are disappointed that their attack has failed. He asks you to come to a Western-style mansion tonight that is rumored to be a "monster's mansion" and steal the treasure, but...

Susumu is about to jump off the roof of a building!? Hiroshi and his friends run to the school, worried that she intends to commit suicide. But Susumu just wanted to fly. Although this commotion ended successfully, information that Matenro appeared at the Space Rocket Research Institute comes in. Matenro dodged the pursuit of the police and flew into the sky!

Today is Hiroshi's classmate Kananari Senkichi's birthday. The five members of the Hadogumi attend a big birthday party held at Senkichi's house, but the presents they prepare are too common and are made fun of. Five people are disappointed. However, at that time, an invisible man appears at the party venue!? He steals the Kananari family's treasure!

Susumu witnessed a housewife, a regular customer of her parents' greengrocer, shoplifting from the store. Susumu tells his father about this, but his father refuses to criticize the housewife's actions. Why is his father silent when his important items are stolen? Susumu, who is not satisfied with this, fasts to show his resistance to his father. However, when he came home one day, something strange happened to his father!?

Satoru suddenly began to wonder how many suckers there were on the octopus' legs. Then Matenro appears and provokes Satoru, saying, "You don't even know about that?" An angry Satoru decides to investigate using an actual octopus, but Matenro steals all the octopuses in Tokyo to prevent Satoru from investigating. What will Satoru do when he is blocked in all directions?

On the way home from school, Yasuko stopped by the botanical garden with Mr. Ochiai. However, Yasuko is disappointed by Ochiai's lack of delicacy. In her heart, a feeling similar to the admiration for Matenro, who always behaved like a gentleman, was growing in her heart. Inspector Karakiri of the Tokyo Metropolitan Police Department appears in front of Yasuko. He was chasing Matenro's crimes.

A videotape was delivered to Hiroshi by Matenro. When they immediately play the tape at the Hadogumi's hideout, they see that it is a criminal notice from Matenro. It is said that he will obtain the "Golden Manju Kannon" at Chikurinji Temple within the day. So, when Hiroshi and his friends asked the Western-Chinese priest of Chikurinji Temple, it seems that the "Golden Manju Kannon" does indeed exist somewhere in the temple...

Hiroshi, Yasuko, and Susumu, who found the "path to the future," disappear. Maybe he was kidnapped by Matenro... While Mr. Ochiai and the three parents were worried, the three in question ended up in the world of 2007 AD. During this period, severe food shortages occurred due to droughts occurring all over the world. Everyone was suffering from hunger.

The world of 2007 A.D. ruled by Matenro, where Matenro turns weak humans into robots and feeds only the strong, or chosen ones. Hiroshi and the three others are finally captured. However, Masao's efforts to communicate with the past world at the request of the three bear fruit, and Takeo and Satoru also arrive in 2007. Now is the time to strike back!

Today, Satoru is on duty to take care of the weapons of the Hadogumi. I had just witnessed Mr. Ochiai making a phone call somewhere, so out of a sense of mischief, I turned my "shoe-on-ser" on and could hear what Ochiai was saying. The teacher is Matenro after all!? Satoru chases after the teacher in order to get definitive proof, but not only does he lose sight of him, but he also breaks the shoe-on-ser...

A burglar broke into Senkichi's house. Fortunately, Chikichi was not injured, but Mr. Ochiai takes this incident as a lesson and tells the students, "When in danger, run away first." The following Sunday, Takeo's father left for Shinshu. Since his father will be away for about a month, Takeo decides to protect his mother in his place. However, Takeo's feelings were a little too strong...

Yasuko sees a magic show by Ten-O, a world-renowned magician, and becomes inspired to become a magician. At the school newspaper's editorial meeting the next day, Yasuko proposes a special feature on magic. He attempts to interview Ten-O himself. However, in reality, Ten-O was a suspect marked by the International Police. According to Inspector Karakiri, Ten-O might be Matenro!?

Hiroshi, who has been playing games at home, realizes that he forgot his homework at school. Hiroshi's father also scolds him, so he goes to pick up his homework even though it's late at night. Then, the vice principal was crying alone in the staff room... In fact, there had been an incident at Takehaya Elementary School where someone had stolen the grades of the upper grades. The vice principal was suspicious of Matenro.

At Yasuko's suggestion, the members of the Hadogumi decide to go cycling. One of the goals is to deepen the friendship among the team. The other was to offer oil to the "Bicycle Shrine" at the request of the owner of the bicycle shop. Yasuko finally arrives at the bicycle shrine, where she is suddenly attacked by bicycle parts. Yasuko is in danger!

Hiroshi was popular with the girls at school. The reason for this, according to Hiroshi himself, is that his "transparent kindness" is effective. In other words, it was all a calculation. Matenro steals Hiroshi's "kindness". Hiroshi loses his "kindness" and suffers. What's more, Matenro orders Senkichi to take away her family's jewels as a condition for returning his kindness.

A series of kidnappings of elementary school students occur. Mr. Ochiai lectures his students on the despicable crime of kidnapping and the mental attitude children need to protect themselves. However, Hiroshi thought that this incident should be resolved by the Hadogumi, so he called the members together after school. The members agreed with Hiroshi on the condition that he would not do anything dangerous. The activities of the Hadogumi begin.

The Hadogumi group is in danger due to the mysterious kidnapping group, the Darkness Clan. The Dark Clan's goal was to find a boy with the perfect talent and have him rule the future of Japan and eventually the Earth. The family is finally deciding on a prestigious successor through a selection test. Hiroshi and his friends were also made to participate in this test. What will be their fate?

The training camp for the Hadogumi has begun. However, on the morning of the second day, Susumu collapses. Surprisingly, Susumu can't sleep unless he listens to his mother's lullaby, and he couldn't sleep at all last night. Susumu is embarrassed when his friends find out his secret. And, as expected, even Matenro found out about the secret. Matenro declares to Susumu that he will steal her lullaby.

Inspector Karikiri and Takeo's father, Shoichiro, were childhood friends. The two meet again for the first time in a long time, hit it off, and have a drink at Shoichiro's house. Shoichiro had just discovered some earthenware in Shinshu and brought it back with him, so he earnestly asked the Metropolitan Police Department to have it examined in detail. As a result of the appraisal, it was determined that the pottery that Shoichiro discovered was a national treasure.

Takeo is obsessed with bird watching. He was flapping in the early summer sky, staring at the birds with sparkling eyes. However, there was a group that was targeting these birds with a slingshot. They are students from another school, the Pachinko group. Takeo protects the bird from them and ends up getting injured. Hiroshi and his friends hear this and decide to take revenge on the pachinko group.

Because Satoru's mother is not feeling well, the restaurant run by Satoru's father has to temporarily close, even though it is Sunday. So, Hiroshi and his friends use this opportunity to make a plan to have Ochiai-sensei and Junko-sensei go on a date at a restaurant. However, the person who came to the store was Matenro, not Ochiai. He offers a "date truce" to the Hadogumi.

In order to capture Matenro, the special training of the Hadogumi continues. However, Yasuko's special training menu was difficult for Hiroshi and his friends. So they consulted Mr. Ochiai. Ochiai called Yasuko and told him to think about the contents of his special training. However, on the way home, Yasuko suddenly travels through time and space to a mysterious village. Yasuko is asked by the villagers to exterminate the White Bone Princess...