Hiroshi has to go on a business trip to Kyushu, so now the entire Nohara family has decided to stay with an childhood friend of Misae's in Asso, Kumamoto.
But when they arrive at Kumamoto Station on their way to Asso, they meet a strange man who offers them an even stranger camera on the condition that they'll act as his witnesses...

With his new camera in hand, Shinnosuke can enjoy his summer vacation in the beautiful Asso fields and mountains to the fullest. The scenery is even crawling with creatures that he would never find in Kasukabe. And there are townspeople to help and new friends to make.
That said...don't these kids look an awful lot like the ones he knows from home?

One cool summer night, Shinnosuke witnesses a giant creature outlined against the light of a full moon. Next to the creature is a strange man with a wide smile.
It's the same weird man who gave him the camera at the station...
And he calls himself the Professor Akuno. Following this encounter more and more strange things start to happen around Asso...

More details on the official game page of Shin chan: Me and the Professor on Summer Vacation -The Endless Seven-Day Journey- ...