some people believe that the ring is almost like a promise ring, since seonho liked myeongi since HS, he may have gotten a ring to promise his heart to him. And when they finally meet up, neither really verbally admits their feelings. Seongho speaks on Myeongi's behalf and they do it, but never anything romantic. Putting the ring on Myeongi's finger was the closest he could get to actually admitting it. Because he finally had a chance to be with him, Seonho gave his promise visually that way. Myeongi understood the gesture the next day, luckily.
some people believe that the ring is almost like a promise ring, since seonho liked myeongi since HS, he may have gotten a ring to promise his heart to him. And when they finally meet up, neither really verbally admits their feelings. Seongho speaks on Myeongi's behalf and they do it, but never anything romantic. Putting the ring on Myeongi's finger was the closest he could get to actually admitting it. Because he finally had a chance to be with him, Seonho gave his promise visually that way. Myeongi understood the gesture the next day, luckily.