I'd understand him being dense, if he'd be madly in love with her. But he simply texts her to be popular with a popular girl he just met. And what he gets are two incoming deadly curses, the same time he got mails from her! I understand why people dislike this MC, as he is a gag-character in a seemingly non-gag-manga setting. I guess they expect, that the author will do one asspull after the other (hidden behind the MC's OP skills), to keep that comedy running and protect him. Because that's what I'm expecting the author to do (more like "fearing" than really "expecting").
If executed well, this can be funny, but up until now it is annoying. His density is on par with him e.g. not understanding, that the light in his room turns on and off, whenever he is using the light switch. And why? Because of p..a kind of relationship, he could have had brought forth in the other world, too. Him not realizing that >deadly curses< have been blocked, that's bad writing/unrealistic behaviour of the MC for the sake of the story and you are losing many readers here because of that. (Also attempted murders make a FMC unattractive in most cases. Just saying.)
That's sooo....sad, because I'd want this spin on the genre to succeed.
That other manga with a similar plot wasn't too bad in the beginning, but soon turned me off. I blame it on descending into honeying all the girls/Making MC far to badass(MarySueLevel). But
this one here is entertaining af!