"A Sign of Affection" centers on Yuki Itose, a college student who is deaf and communicates primarily through sign language. Her life takes a turn when she meets Itsuomi Nagi, a multilingual and adventurous classmate who is fascinated by languages and cultures. Itsuomi, who is fluent in multiple languages, becomes intrigued by Yuki's use of sign language and begins to learn it to communicate with her. Their interactions grow as Itsuomi’s curiosity and kindness bridge the gap between their worlds, fostering a deepening connection.

The narrative explores their evolving relationship, highlighting the challenges and nuances of communication, particularly in a world where Yuki often feels isolated due to her hearing impairment. Itsuomi’s open-mindedness and determination to understand Yuki’s perspective create a foundation for mutual respect and affection. Alongside the central romance, the story delves into themes of self-discovery, independence, and the importance of empathy in human connections.

Supporting characters, such as Yuki’s childhood friend Rin and Itsuomi’s friend Oushi, add layers to the story, providing contrasting perspectives on relationships and personal growth. Rin, who has feelings for Yuki, struggles with his own emotions as he watches her bond with Itsuomi. Oushi, on the other hand, serves as a grounding presence, offering insights into Itsuomi’s character and motivations.

The plot progresses through everyday moments and meaningful encounters, emphasizing the significance of small gestures and the power of understanding. Yuki’s journey is one of gaining confidence and embracing her identity, while Itsuomi learns to navigate the complexities of love and communication. The series balances lighthearted moments with emotional depth, creating a heartfelt portrayal of two individuals learning to connect in a world full of barriers.