Cheng-hsin and Yen-cheng are good buddies though they have completely different personalities. Yen-ni is Yen-cheng's beloved little sister, and Cheng-hsin treats her like his own sister too. But the good times they share have to end when Cheng-hsin moves away suddenly in his second year of high school. The brother and sister hardly hear from Cheng-hsin until ten years later, when Yen-ni becomes a freshman at university and Cheng-hsin's new neighbor by accident. Yen-ni finds out that the gentle Cheng-hsin has a heartbreaking secret which makes her want to be his guardian angel...
a Pisces who is easy-going, nice to everyone, and never seems down. Only Wang Yen-cheng and his family know about his problems at home.
a cheerful Sagittarius who has many friends but has never been in a romantic relationship. After accidentally finding out about Cheng-hsin's secret, she decides to be his guardian angel and, eventually, falls in love with him.
a Capricorn who is calm and collected, kind and considerate. But he lacks self-confidence and tends to overthink things. He can seem a little square and serious, but it's because he only shows his true self to those he trusts.