Being a fan of one punch man (obviously) I also love another series of the same author: mob psycho 100.

In both series the protagonists suffer emotional problems, as do link. Saitama gets depressed and feels empty.

Mob, the protagonist of mob psycho 100, is a 8th grader who has little to no talent in anything, in fact, he's lackluster in strength, intelligence, and looks ridiculously plain. And he's a ridiculously powerful psychic. Because of his inability to express emotions as well as other people, his emotions end up building up as stress, which is dangerously released as psychic power when he reaches 100%.

Link feels the pressure of his duty and hides his emotions. He doesn't know how to properly handle him (bottling up emotions is not a good way to handle stress). I found these two characters to be somewhat similar in their struggle to process their emotions.