I don't like open endings. However, the fact that the twins were left behind and MC felt the breeze once he reached the top, I think was positive for MC in regaining his sanity and realizing that his choice to "give up" was wrong. If even just one of the two brothers had followed him, MC would have continued to live tied to the same people who abused him, but this way he's free again... For me, it moved on. (Not a bad story, but I felt the ending was a bit rushed.)
The dynamic between the two is beautiful, they create a nice contrast. The protagonist is too naive, but I didn't mind him, because he has courage and can stand on his own. I would have liked to see much more. ╥﹏╥