Belok Kanan Barcelona follows the intertwined lives of four close high school friends -Francis, Retno, Farah, and Ucup- who have been navigating a complicated web of unrequited love for years, choosing to prioritize their friendship over confessing their true feelings.

The dynamics are as follows: Francis loves Retno, but Retno repeatedly rejects him, citing the need to protect their friendship. Farah secretly loves Francis, but she keeps her feelings hidden because she knows Francis is still devoted to Retno. Finally, Ucup is in love with Farah but keeps silent, knowing her heart belongs to Francis.

The unspoken tension comes to a head when Francis, who has moved abroad, announces his engagement to a Spanish woman named Inez and invites his three friends to his wedding in Barcelona. This news forces the trio to confront their past. Retno, who lives in Copenhagen, is heartbroken. Farah, living in Vietnam, decides she must finally travel to Barcelona and declare her love for Francis before it is too late. Ucup, based in Cape Town, races to Barcelona as well, determined to stop Farah and chase his own chance at love.

The film follows their separate, globe-trotting journeys as they converge in Barcelona, forcing them to confront harsh truths and chase their respective loves before the wedding day.