What episode is Doraemon's secret cabin in Houshan? Why is the back hill called the secret back hill?

Daxiong used the portal and the president of that company to send it to the small mountain village where he lived when he was a child. He took a look at the hillside and recalled the happy scene of playing on this mountain when he was a child. May be moved by the scene in front of me, so I stopped the plan to develop the back hill.

The back hill of this school is just the entertainment place for Daxiong and his friends in their childhood, which is the same as the open space. Daxiong and others often chat on the back hill to enhance their feelings, which is also the best place of origin. When Daxiong is bored or upset, one of them will run to the back of the school for a turn. Friends sometimes play hide-and-seek here and spend a happy childhood together.

In fact, this type of animation like Doraemon is rare in the second world. Whenever they are bored or have something new, they will brew on this mountain when planning. In fact, the author created this place to make it more secret and convenient for aliens to appear in the future. It would be strange if the aliens behind the school swaggered around the city.