のらくろクンのおじいちゃん、のら山くろ吉は、多くの戦争で名を馳せた歴戦の兵士。戦友たちとの再会をきっかけに「若いもんには負けられん！」と一念発起、持ち前のバイタリティとこれまでに培ったノウハウを活かすべく、「のらくろ探偵事務所」を設立する。

のらくろクンは、大家の息子・圭太やお隣に住む女子高生のリカと共に探偵稼業を手伝うことになるのだが、事務所に現れる依頼主は孫悟空にクレオパトラと多種多様。元気いっぱいのくろ吉と、ひたむきだけどドジなのらくろが、まわりを巻き込みながら今日も珍事件に挑む！

田河水泡の『のらくろ』を現代風にリメイクした作品。主人公にくろ吉の孫を迎え、舞台を現代の人間社会に変えた、楽しさいっぱいのファミリーコメディ。

以田河水泡原作的《黑野良》为基础，改编成为具有现代风格的重制作品。曾经在军队里工作的“最早的黑野良”野良山黑吉的孙子黑野良君住到了圭太的家里，在日常发生的种种事件中快乐幸福地生活着。

October, 1987, Autumn. In Suganami, Tokyo, there lives the Kinoshita family whereby the father draws very little pay out of his job as an ordinary salaryman. In order to cover expenses, he decides to let out the second floor of their apartment to earn additional rental income. One day, an obstinate-looking eldery dog, accompanied by a younger boy-dog, came knocking on their doors. The eldery dog addresses himself as Norayama Kuroyoshi and introduces his grandson as Norakuro. The former wants to open a detective agency and intends to rent the unit for their office. He will be the president of the investigative bureau while Norakuro-kun will be the director. He will also recruit one of the Kinoshita's sons, Keita-kun, as his employee and their advisor will be the girl-next-door, a high school student by the name of Rika Sawaguchi. On the third day since the official opening of the office, the telephone rang, a signal of a new case.