"Susume! Gachimuchi 3-kyōdai" centers on three brothers—Aniki, Chū-nii, and Shōta—who share a unique bond rooted in their passion for bodybuilding and physical fitness. The narrative explores their daily lives as they navigate personal challenges, relationships, and their shared goal of achieving peak physical condition. Aniki, the eldest, serves as the group’s mentor, embodying discipline and strength. Chū-nii, the middle brother, balances humor and determination, often acting as a mediator between the siblings. Shōta, the youngest, is eager to prove himself, striving to match his brothers’ accomplishments while carving out his own identity.

The series unfolds through a series of episodic adventures, blending comedy, drama, and moments of introspection. Each brother faces individual struggles, such as Aniki’s pressure to maintain his leadership role, Chū-nii’s quest for self-confidence, and Shōta’s journey to overcome self-doubt. Their interactions with supporting characters, including rivals, friends, and mentors, add depth to the narrative, highlighting themes of perseverance, camaraderie, and self-improvement. The brothers’ shared dedication to bodybuilding serves as a metaphor for their personal growth, with their training sessions and competitions providing a backdrop for both lighthearted and poignant moments. The story maintains a balance between humor and heartfelt storytelling, offering a relatable portrayal of sibling dynamics and the pursuit of individual and collective goals.