trying to save them =/= forgiving them.
MC have an idealistic thought of what an adventurer is, and that's why he want to become one, can't really blame him for sticking to it.
So this is what i gather.
his wish: for her to get cured.
his payment: that everyone forget their time together (including him, I guess ).
her wish: so he would never forget her.
her payment: maybe she is the one who ended up forgetting instead.