Oops, I Fell in Love with My Best Friend's Brother

The female lead should be gentle and thoughtful, perhaps named Su Wan. She and her best friend have known each other for years, giving them a solid foundation. Her best friend, Lin Xi, is lively and cheerful, which complements the female lead and also gives them a natural way to introduce the male lead. He is Lin Xi's older brother, Lin Yu. He should have a contrasting side to him, perhaps seeming cold on the outside but warm within. He could be an architect, giving him a mature, dependable air befitting an older brother. An age gap of four or five years would be just right, not so wide that they feel distant. The story of what happens between them