Bruh, this chapter is a visualization of what could have been if he chose a different life.
If he didn't choose climbing he wouldn't have been so lonely.
It's not that deep, the title even givès a hint.
Damn, I love that this manga gets psychologically deep, and to even express certain feelings like loneliness without using a single word of dialogue. One of the reasons why I can't put this manga down!
This chapter hits like a brick. Every now and then I catch myself thinking about it, even years after I've read it.
It was one of the two times I cried reading a manga, the other being Ashita no Joe's ending.