Are the Mountains Sunny?

A helicopter in the sky reminds Houtarou of the teacher Ogi of his junior high school days. Houtarou has assumed that Ogi likes helicopters because he saw that Ogi had a relieved smile when Ogi found a helicopter through a window during a class. But, Satoshi tells him Ogi wasn't interested in it. Houtarou is curious about why he smiled at that time.