This boy has balls of adamantium.
Haro has been lucky enough to discover his purpose in life at a very young age. As he explains in chapter 3, his authentic self is an artist who captures moments of beauty on canvas, and as long as he can do that, social ostracism and ridicule just don't stick to him. It's a very spiritually enlightened state of mind that few people reach at his age.
Also, the episode with Nakamura shows that it's not so much physical nudity that sparks Haro's desire to paint as emotional authenticity. When Nakamura was pushing herself to stand in front of him naked, she was following the script her classmates handed to her ("man-eater bitch"), but the moment she has shown her true emotions, how much she was hurt by libel, Haro immediately recognized it, from just her face, no nudity involved (even if he did add it to his final painting of her, which I found kinda strange). Accordingly, we can infer from his reactions to Kamio that she is someone who is true to herself and perfectly comfortable in her own body at all times. I have known a few people like this IRL and they always have that feel like they are 100% there, whereas everyone else around them is at 50%, tops. Not sure if that makes sense.