Owen's design seems fine, and is one of the cutest characters. My favorite characters in the VN so far are Owen and Vlad.
Usually a character can be visually appealing even if fat so long as weird proportions are avoided such as when people give a character thighs and hips that are massive compared to the upper body (e.g., when the thigh and hip width starts to extend beyond the shoulder width which is a shape profile often linked with lipodemia in mammals). Thankfully many artist that do that kind of hyper art, tend to limit it to female characters while not ruining the male characters with it.