Responses

I don't think the anonymous person was there, unless if it is one of the two guys, who were fucking. if you look at the two photos, you can see the MC's hair on one of the pictures, so it's not the opposite camera, but a weird angle that he took the photo from. Also, I believe the mangaka probably struggled a bit on how to draw it properly.
His friend deleted the photo, so he never found out about it. Also, you can write without looking, but it would have been more realistic, if there had been a few spelling mistakes.
???? this last chapter doesn't make sense. the mc went to take a selfie of his face... but accidentally had the other camera on or smth... but he was sporting a peace sign for the opposite camera... and he can't fuckin see bc of the gauze, but he sent a whole paragraph to hatsuka... he didn't notice the other two fucking even tho he took a picture of them?? this chapter made No fucking sense.