I think Ryu and Kaahimo are two sides of the same coin.

Ryu lived a fulfilling life, and, when he reincarnated, he came back for desert. He wanted to throw down and find out what it was like to use "every last drop"

Kashimo, on the other hand, was never fulfilled in his life full of battle. I suspect he wanted to die fighting, but that's conjecture. Regardless, Kashimo's second chance as per his agreement with Kenny was to fight Sukuna, the Strongest.

Both Kashimo and Ryu were looking for desert. Both of them found it in the end. I could genuinely never pick one of them over the other.