@Jojeke man, let me tell you something.
Pls, read the name of this manga. Then read it again. And read for the third time, so you would understand for sure.
This manga is not about Manabu. It's called "Amano Megumi", for Christ sake! Why 99% of readers dont understand this, and think that MC is Maa-kun, and he is so lame etc? This is manga about girl in love, who is to afraid to confess, who is looking for the excuses to do it "some time after, no it's not a right time". And we are looking at her through the glass of Maa-kun, who just cant think that she is interested in him, bcs he is a nerd without friends, when she is the star of their school she is gorgeous, and HE UNDERSTAND THAT, he is a man, after all, so he is always frustrated like "you should be more careful", thinking that she is always like that, when in reality - she is like that only around him.
I mean yeah, for sure - we need some event that will show us, readers, that he realised his feelings for her, BUT - I dont think that it will be before Amano confess to him. So - one, who need awakening - is our MC - Amano - and it is HER who would be affected (and already is, we saw it from previous chapters) by this new girl in the story, and who finally need to understand, that is she will slow things down for too long - someone would steal her man from her. You see, the only way in this situation, that HE would woke up - it's as you say - if new boy would intervene and hit on Amano. But - we see - this is not the case.
So - the next thing we will see, and I'm sure, awakening of Amano, not Maa-kun. My guess - in future chapters it's her, who will finally confess, he will said like "we are only friends, I didn't think about you that way", they will graduate, and only in uni, after seeing this Misava he will realise, that he dont love her anymore, she was just some goal, dream, but instead the only one he missing - is Amano. I'm even think that in the end she won't apply to the Tokyo U after rejection, and will go somewhere else.
That's how I would've write this to connect all the dots - its fit in perfectly in the story style.
And they are already in the graduating class, so, I think, this will end ~in 50-70 chapters, maybe less. Well, at least i hope so - even though I love this two dorks, I dont wanna see this stretching out for another 5 year of their university studying 😂