"he's making his move again" so he's tried multiple times to get with Oosawa.
This is just the second time—Ono previously complimented Aya on her dress at the prom, then Mitsuki arrived and he was left in the dust. It’s implied that the reason the Aya-Mitsuki Protective Squad even notices what’s happening is because Ono is known to be shy and bit oblivious.
Most likely. Tho, with how Nakajima expresses it, Ono may have approached Aya other time off screen as well.
Well, no—Ono literally breaks the 4th wall to remind the audience who he is and what he did at the prom and explains that he has been “cramming Western music” since it was all “left up in the air back then.” This chapter he’s trying again.
Yeah, I see what you're saying. I think I just read too much into Nakajima's comment, as it'd be weird to stress on the "oh there he goes again" if it was only one other time. But, that's probably just how he rolls, just overselling stuff.