Nao is very meh part of the story imo. I can understand where he's going at but he was never a character I felt invested in.
If he was too likeable though, most of us wouldn't be rooting for Matsunaga-san—not that the age-gap debuff (or buff, I've met 50/50 people on this) was with him already (fyi, I've known people who care more about age than character and deeds).
Author really had a hard time with him, huh. Oh well, bye-bye Nao-kun. That was a dick-move you've did as a kid but I did like your farewell and monologue than most 2nd MLs. I've seen worse.