100% it's for Koguma - the question is whether Hino knows she's being followed. Kinniku is good at twisting expectations and I think he thinks we think that Hino knows, so maybe she doesn't? Real short chapter though. The wait for the next is going to be harder.
I think I would like it if Hino-san really wore super girly and or cosplay clothes outside of school too! But I think either she spotted them tailing her and is teasing them- or she is buying it for Koguma.