Reread 2011. In which Watanuki is bad-ass.
Watanuki saves the ame-warashi with a piece of broken glass. Dômeki gives up half of his eye.
There is a slight epilogue where a lightning-spirit electrocutes Watanuki and then gives him a fireworks display. Dômeki can see through Watanuki's eye. Watanuki realizes that Himawari ships Watanuki/Dômeki.
nb: circles motif when ame-warashi heals Watanuki in pure water