Woojin likes Kyung in the first place, it shows the way he look at him in the earlier chapter. Kyung thought that Woojin likes Inseob, because Woojin let him misunderstood whom he really likes. I think Kyung became curious about Woojin because he thought he likes Inseob and since then he always looked at him and be conscious about everything he did. And it makes him angry that Woojin is still in love with Inseob (which is not). Kyung only confesses to Inseob just to provoke Woojin. He does everything even "competing" who get Inseob first, he doesn't really have feelings for him, everything he did was to provoke, to get Woojin's attention, to get close to him and make him "forget" Inseob. So yeah that's it. One is pretending that he likes the other guy, while the other one believes it.
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