Satou is shy and insecure about her looks and smarts, the "net guy" is suspicious as fuck, he clearly know how to take pictures and kept encouraging her to take it, despite her insecurity but not sharing his own, this smells like pedophile grooming his victim.
Satou telling Yamaguchi she loves "net guy" despite him not meeting her and cancelling their meeting "really late" after their scheduled first offline appointment, this girl gonna be abused, he definitely should step in.
Now that Yamaguchi heard Satou and finally understood his feeling towards her, seeing how determine she is in her love to "net guy"... this is pain...
Thanks for the scanlation!