"Tomodachi 100-nin Dekiru kana" centers on Kenta Hasegawa, a high school student who struggles with social anxiety and a lack of friends. After transferring to a new school, Kenta resolves to change his life by making 100 friends, a goal inspired by a childhood memory of his late grandfather, who encouraged him to value human connections. The narrative explores Kenta's journey as he navigates the complexities of forming friendships, overcoming his insecurities, and learning to communicate effectively with others.

The story unfolds through Kenta's interactions with a diverse cast of characters, each with distinct personalities and backgrounds. Key figures include his classmate Yūki, who becomes his first friend and helps him break out of his shell, and Rika, a confident and outgoing girl who challenges Kenta to step out of his comfort zone. As Kenta gradually builds his circle of friends, he encounters various social dynamics, such as misunderstandings, rivalries, and moments of genuine camaraderie. The manga delves into themes of self-improvement, empathy, and the importance of human relationships, portraying both the challenges and rewards of forging meaningful connections.

Kenta's progress is not linear; he faces setbacks and moments of self-doubt, but his determination to achieve his goal drives the narrative forward. The series balances lighthearted, humorous moments with more introspective and emotional scenes, creating a nuanced portrayal of adolescence and personal growth. Through its exploration of friendship and social interaction, "Tomodachi 100-nin Dekiru kana" offers a relatable and heartfelt depiction of the struggles and triumphs of building relationships in a modern high school setting.