TV-Series
Description
Zhen Kaixin, called Kai Xin, is Shi Fen's closest companion. His name meaning "Happy" or "Joy" reflects his inherently cheerful and optimistic nature. He radiates warmth and positivity in social settings, actively striving to uplift others during hardships. Though generally lighthearted, he exhibits situational awareness during serious moments, preferring to focus on constructive solutions over negativity. He typically sidesteps unnecessary conflict yet remains steadfastly supportive when friends need help.

Kai Xin shines as the star player on his school's basketball team, displaying deep passion and dedication to the sport. This pursuit fuels tension with his disapproving mother, who pressures him toward conventional academic careers like medicine or law. His father remains largely absent due to work. This parental dynamic culminates in a major conflict after Kai Xin and Shi Fen are caught cheating on an exam. His mother demands he sever ties with Shi Fen and quit basketball after the season, threatening school transfer. Fearing the loss of both basketball and his best friend, Kai Xin initially complies by ignoring Shi Fen.

Shi Fen's persistent attempts to reconnect spark an argument that escalates physically, resulting in Kai Xin accidentally falling down stairs and breaking his leg. Confined under strict supervision, he is forced to watch the season's final game from the sidelines. Witnessing Shi Fen join the team as his substitute and recognizing her son's profound dedication, Kai Xin's mother relents. She permits him to continue basketball and maintain his friendship with Shi Fen, conditional on added daily study time. This resolution restores his ability to pursue his passion alongside his friendship.

His interactions frequently involve comedic scenarios stemming from his association with Shi Fen. One notable incident involves them pretending to be a couple to secure seating at a fully booked restaurant, leading to exaggerated romantic gestures from Shi Fen that cause Kai Xin significant embarrassment when their deception fails disastrously. Despite such outcomes, he typically shares laughter with Shi Fen over the absurdity afterward. Kai Xin also forms an unexpected bond with transfer student Wan Sui, finding himself mediating between Wan Sui and Shi Fen during their initial rivalry. His presence fosters group cohesion around the Shi siblings.

Kai Xin's character design features distinctive hairstyling and casual attire, visually setting him apart. His voice performances convey characteristic cheerfulness and occasional flustered reactions, reinforcing his role as an optimistic counterbalance within the group.