While the idea to have this specific OVA focused on another character was full of potential, I feel like it was not done as well as it could've been. Getting to experience the story through Kimura's perspective was interesting but the changes made on the typical fight preparation on top of that made the episode fall a little bit flatter than it could've been, especially in exploring Kimura's side of the relationship with the rest of the gang (the relationship with Aoki being a bit of an exception), which made the first half of the episode feel a bit disjointed.
Furthermore, what really brings this OVA's rating down for me was the ending, that basically invalidated a good chunk of the emotional weight of the episode, that could've been used to add an interesting twist in the Kamogawa's Gym dynamics.
On the positive side, the fight in itself was one of the best so far in the anime series, and the animation felt more on par with the original Hajime no Ippo series, which I personally prefer.
