This kanji shows a square flag waving in the wind. Among the different kanji for “flag,” this one specifically means a square war banner used to rally soldiers.
flag(square) (旗)
travel(旅)
The origin of this character is quite fascinating. It depicts two people walking toward the left, right in front of a tall, grand pole bearing a large flag. In ancient times, people on a journey would travel exactly like this—marching together under a massive flag.