And not much to go on.
I've encountered the arc numerous times in romance literature, all romance literature in every culture: one member of the couple (or both) has been hurt in love: turned down repeatedly, abused, mocked, dumped, and so on.
Everyone can relate. Consider the magnificent "Rose." People get hurt, creep away, consider whether or not to risk their hearts again.
I'm not against the theme. I'm just not particularly impressed by the storyline.
The problem? It is rather like a happier version of the Titanic (a ship is heading to New York...and goes down!). The main character doesn't want to trust again...and does!
So?
For example, in Dorothy Sayers' Harriet-Peter romance, Harriet--who lived with a jerk and then got put on trial for murdering him--is justifiably untrusting of relationships in general. She feels wrung out, fearful of being taken advantage of, wary of Wimsey's strong personality that might overwhelm hers. And what she goes through is powerful but by itself, it would be...honestly, like a lot of naval-gazing contemporary literature. And some manga that never seems to go anywhere.
Luckily, Sayers wrote mysteries! In Have His Carcass, Harriet is forced to face the gap between her strong personality, which motivates her to investigate despite the potential negative fall-out, and her fears. In Gaudy Night, Harriet finds balance in her life and makes a choice to leave a safe haven--which Wimsey has restored to her--in order to tackle the ups and downs of an emotional relationship.
In manga, the Never Let Go series by Saki Sakimoto produces an omega who has every reason to distrust relationships (his family kicked him out of the house when he was a teen). The second volume almost goes too far down that rabbit hole (how many times can people run away from arguments?) but stops short because the non-trusting character is able to take a stance on how the relationship should function in terms of what the couple does: take trips, visit parents, divide up chores. Concrete events are on the table.
Here is the dirty little secret of this problem: reassurance, protection, support is wonderful. But it will never be enough to conquer the fears. The protagonist has to make it happen, and in literature (and film), "make it happen" = action.
Have a character learn to trust by all means--but make sure they learn while they are doing other stuff or by doing other stuff.
