oh, my ;_; What a beautiful story you wrote. That duality of best friend/worst enemy is one of my favourite tropes wherever I read it. I think it speaks deeply about how we relate to those closest to our hearts, how we give them power over ourselves, delivering our beings into hands we expect to be kind but can be equally as unkind because that's just how life turns out sometimes.
The ending was really vivid, I could completely picture old Mr Ren giving himself into the current as he gave himself first into the hands of his friend, and then into his path towards his own version of reconciliation.
Thank you for reading it. Yes you saw so much of what was in my mind.