The story is about bodyguard and the idol. The idol had tour on korea and the uke(bodyguard) become one of the bodyguard of events. The bodyguard were asked by his friend/sister to get the signature of the idol when the bodyguard asking for signature the idol mocking up him in english and surprisingly the bodyguard now about english and going off and mad. That's all i'm remember. Thanks
http://www.mangago.me/read-manga/knock_me_out/
matches your description
Don't get me wrong i'm really happy for ho-in and chunwo but something about their relationship is not sitting right with me, well either way i hope that's the best for them