It seems to be a bit confusing. Eric even says he felt happy when Ren covered for him, which kinda hints at maybe he actually did it? OR, he’s just implying he’s happy that Ren is defending him.
On the other hand, blue hair guy supposedly smiled when Ren got hurt and Allen suggested that it was probably him who did it.
So…I don’t think it was ever 100% confirmed lol
He was happy that MC covered for him and still spoke to him even though the signs pointed at him being culprit which wasn’t the case, it was James. The ML mentioned seeing James acting suspicious and scared that same night and how he was loitering anxiously around the trashcan where he found the USB. The fact that he smirked and was happy MC got hurt just further proves he truly did not like MC and wanted him to get hurt/in trouble. Based on that, the author is telling us it wasn’t Eric, it was James.

Did yall forget Eric is the one that tossed his USB in the trash? Hours of hard work almost went down the drain