Trope
Grumpy Sunshine
One scowls. One glows. Both are doomed.
3 books on this shelf, newest first.
Grumpy–sunshine pairs someone who has given up on people with someone who refuses to. The appeal is not the contrast itself but the direction of travel: the grump softens in private, long before either of them admits anything has changed.
Where to start: Contemporary romance and cosy fantasy do this best. Watch for books that let the sunshine character have real depth — the trope falls flat when one half is only there to be cheerful at the other.