Books like Shadow of Colossus/Ico

[Nijhia]

So, I am basically looking for a book that covers something like a lonely adventure, possibly a love story, a big bad that seems good. Basically, what happens: there is a boy and girl, the boy usually saves the girl but there is a price for it and it is usually really awful, bittersweet memory.

[...cats?]

I don't know if any of these books have the exact dynamic you're looking for, but:

The Cabin at the End of the World by Paul Tremblay is about apocalyptic doomsayers who tell a couple and their daughter that if one of them doesn't die, the world will end

Black Leopard, Red Wolf by Marlon James is a high fantasy novel where the main quest imposes heavy costs on the romantic relationships the characters have

Die by Kieron Gillen involves characters having to sacrifice their loved ones in order to protect themselves