Toshiyuki and his wife, Chiyoko, run a store named “Fukunoya” in Fukuoka. They become friends with a takoyaki (octopus dumpling) stall owner named Tsuru and try to help her out, as does the rest of the kind-hearted community.
An anonymous letter is delivered to the Tokyo Metropolitan Police Department. The letter states that a criminal of a murder case will appear at the countdown party Masquerade Night that will be held at Hotel Cortesia Tokyo. Detective Kosuke Nitta must go undercover and work again at the Hotel Cortesia Tokyo. There, he meets Naomi Yamagishi, who works as a concierge. Without any information about the criminal, except that the person will be in attendance, Detective Kosuke Nitta works feverishly to find the criminal among the 500 attendees.
Ryuji (Taisho Iwasaki), Satoru (Ryuga Sato) and Atsushi (Hidaka Ukisho) are friends in high school. They are classmates in the 2nd grade class B. They appear like troubled students, but they are not. They are actually country boys. When they are at their secret place, they suddenly feel a big shake and hear the sound of thunder. Then next moment, they see a man Sanpei wearing a dirty military uniform with a backpack and holding a bayonet. Sanpei came from the past, right before the end of the war in Guam. Ryuji, Satoru and Atsushi enjoy their time with Sanpei. They think that being with Sanpei, their lives might change and they ask him to spend summer with them. Class President Michifumi (Yuto Nasu) and twin brothers Akihiko (Naoki Fujii) and Kazuhiko (Issei Kanasashi) join the group.
Based on the TV series from the same name, Mentai Piriri stars Hanamaru Hakata, the icon of Hakata, Fukuoka, alongside Yasuko Tomita, who both starred in the television show playing husband and wife respectively. With additional scenes not depicted in the original show.
A variety show where the comedy duo Hanamaru-Daikichi travel around Fukuoka Prefecture, interacting with locals. The show features location shoots, with occasional studio segments for special episodes.