I think when Naruse said "it's not of your business" didn't mean what happened with him and Yuna but the reason that happened for.
And it's not like he tried to hide it but it was nothing to him. (Just how Yuki hide 3 hugs from Hakamada and one from Suwa from him because they were nothing to her. )
I hope that fans can control their emotions and be understanding and not hate on him like that when they know everything. 😅 (Yuki too)
I don't really think it's that bad, they're young and Human, - they lack things, miscommunicate, get angry, jealous and so speak in the wrong way, but they're in their beginning way and can solve this by talking, maturing, feel each other.. etc