Our Universe follows Woo Hyun Jin, a hardworking job seeker longing for a stable future, and Sun Tae Hyung, a free-spirited photography assistant who values his independence. Although they become in-laws when their older siblings marry, the pair never get along and constantly clash over their different personalities and outlooks on life. Their relationship takes an unexpected turn when tragedy strikes and their siblings pass away, leaving behind a young son who suddenly becomes their responsibility.
Forced to live together and raise their orphaned nephew, Hyun Jin and Tae Hyung must learn how to navigate the challenges of co-parenting despite their constant bickering. As they face sleepless nights, family struggles, and the realities of raising a child, their misunderstandings begin to fade and an unlikely bond starts to grow. What begins as a reluctant partnership gradually blossoms into a heartfelt romance, as two people brought together by loss discover the possibility of becoming a family.