The film revolves around three boxers from different backgrounds. Akira Mino (played by Mirai Moriyama) has fallen from his peak as a professional boxer to become a marginal underdog, always seen as a "soft persimmon" to boost others' confidence. He once lost himself and even thought about giving up boxing, but after hitting rock bottom, he has a sudden realization and ultimately returns to the ring in an attempt to find the meaning of survival. Ryota Omura (played by Takumi Kitamura) is a young boxer carrying a secret; abandoned by his parents in childhood, he ended up on a rebellious and troubled path. His shattered life finds new hope through boxing, as he emerges determined and unstoppable. Shun Miyuki (played by Ryo Katsuji) is a second-generation star and comedian. Under his father's skepticism, he gets lost and struggles to find his place. Participating in a boxing match as part of a TV program企划, he aims to prove himself through boxing while maintaining a facade of humor and levity. "Underdog: Survival" primarily centers on the ultimate showdown between Akira Mino and Ryota Omura. After his match with Shun Miyuki, Mino faces the decision of retirement once again, meanwhile, a new star, Ryota Omura, determined to showcase his skills in the boxing ring, suffers an injury just as he begins...