Well, being young and awkward is a very normal response. He's been forever in love and thinks Haruna is straight. Still, he can't stop himself from hoping something could happen, that's why he grabs onto the little things Haruna says, like "I'm happy when Nao is there".
On the other hand, Haruna told Nao he likes a girls and he is continuously seeing them together smiling (especially bc Maeda is after Haruna). So obviously he is hurt. Nao wants to just be done with that pain by resigning that love under the pretense of "he has a girlfriend, so there is no place for me". Instead, he is being prioritized by Haruna, with the menace of him been taken by some girl and him just being a friend.
It's the uncertainty that eats anyone alive, so Nao just wants them to be together instead of suffering through that. (ㆁωㆁ)
In the second story, why is nao actively pushing his friend to that girl? Like it's so dumb. I get that he thinks his love isn't reciprocated but they are still best friends, that counts for something. His friend said he likes her but when she asked him out, he didn't wanna date her, but Nao is acting like their cupid, lol. Distancing him, sure that makes sense, but not the other stuff.