I was wondering abt this too, i ended up making my own conclusion that they might have broken up because they're focusing too much at work and not to each other then they kissed and make up hehe
I'm going to guess that Kyusung helping his sister was a new development. So Jooha assumed
that makes a better sense lmao
Actually the author did explain it in her Q & A because someone had asked the same question!! Go back to the chapter "afterward" and the question starts with "Will there be a side story for the side couples ji kyusung and Yeon jooha?" She gives a brief run down on them!! :))
in the afterword of s2…the author explained that Jooha became depressed and had poor self esteem after his accident to the point where he felt jealous about Kyusung with other ppl (hes working) nd so jooha broke up w him but still came back w each other (▰˘◡˘▰)
Did I miss something? Did they ever explain why Jooha thought Kyusung was seeing someone else? Or why he said that