I think it was Jihwa's spy who caught them (the one from chap 12-13). Probably, Jihwa ordered him to keep an eye on them since he wasn't so happy with the idea of them being alone together(Yoon and the painter). I don't think it was the teacher because he isn't that stupid, he already knows the rumors and I believe he wouldn't do something so stupid that might make him loose his golden opportunity.
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I think it was Jihwa's spy who caught them (the one from chap 12-13). Probably, Jihwa ordered him to keep an eye on them since he wasn't so happy with the idea of them being alone together(Yoon and the painter). I don't think it was the teacher because he isn't that stupid, he already knows the rumors and I believe he wouldn't do something so stupid that might make him loose his golden opportunity.
P.D Sorry, my english isn't that good.