@StaK I'd say with Gojou him not understanding her crush on him is more understandable then most other manga/anime. He grew up with no friends, no siblings, he didn't read manga or books, didn't watch TV/anime, and didn't play video games our boy has an extreme lack of experience with social ques and his heavy nerves in situations, ie being overly self conscious, which is why Marin is a good match for him. She is the popular beautiful social butterfly that we see in the tropes of these awkward guy popular girl relationships but she is also a huge otaku so she knows the "character type" Gojou falls in so she knows it will take a bit for things to get to where she wants but its her understanding of that is why she isnt actively pushing for the relationship yet, she want to be closer friends before she tries for a real relationship, she knows she'll likely have to make the first move.
Its all of this that make them the perfect match, a big part of their growing friendship to relationship is her helping Gojou break out of his shell and become more confident