There really is no helping this mc into seeing takamine-san has feelings for him and it's not teasing/him still being blackmailed. It took literally 1-2 sentences for eri to figure it out when talking to takamine-san. This is taking the phrase "you're blind to what is closest to you" to a whole nother level.
But hey, takamine-san is taking an unusual method, so maybe she should swith it up considering she's dealing with a black hole.
And to the people still on about the blackmail, while I agree it was in poor taste, it's kinda hard to see any other way to get the the black hole's attention to the point where the could be in constant contact. Dude viewed himself as a literal nobody to the point where anything she woulda done, he woulda dismissed it as something else. Like I said, he's a black hole.