"Darling wa Gaikokujin" centers on the romantic and cultural dynamics between a Japanese woman, Kurusu Hana, and her foreign boyfriend, Alex, who hails from the United States. The narrative explores their relationship as they navigate the challenges of cultural differences, language barriers, and societal expectations. Hana, a reserved and traditional Japanese woman, finds herself drawn to Alex's outgoing and straightforward personality, which contrasts sharply with her own. Their relationship begins with a chance encounter and gradually deepens as they learn to understand and appreciate each other's backgrounds.

The story delves into the everyday experiences of an intercultural couple, highlighting both humorous and poignant moments. Misunderstandings arise from cultural nuances, such as differing communication styles, social norms, and traditions. For instance, Alex's directness often clashes with Hana's more indirect and polite manner of expression, leading to comedic yet relatable situations. The manga also addresses the pressures Hana faces from her family and society, who are initially skeptical of her relationship with a foreigner. Over time, her family begins to warm up to Alex as they witness his genuine efforts to adapt to Japanese culture and his commitment to Hana.

Alex's character is portrayed as a well-meaning but sometimes clueless foreigner who is eager to embrace Japanese customs, often resulting in endearing blunders. His enthusiasm and willingness to learn about Hana's culture serve as a bridge between their worlds. Hana, on the other hand, grows more confident in expressing her feelings and asserting herself, breaking away from the more passive role expected of her in traditional Japanese society. The manga balances lighthearted moments with deeper reflections on identity, love, and the complexities of cross-cultural relationships.

Supporting characters, such as Hana's friends and coworkers, provide additional perspectives on intercultural relationships, offering both encouragement and skepticism. These interactions enrich the narrative by showcasing a range of attitudes toward foreigners and international romance in Japan. The story progresses through a series of episodic chapters, each focusing on specific cultural clashes or milestones in Hana and Alex's relationship, ultimately painting a vivid picture of their journey toward mutual understanding and acceptance.