What is this Kpop song?

I don't remember the name of this song. :( Can somebody help me? 

In the video, there is a boy and a girl. They are texting each other, and I guess they're trying to meet, and they seem to like each other. If I remember correctly, in the end they are able to meet. 
+ Bonus hint: at one point the boy, while in the buss, falls asleep and dreams about the girl. 

Overall the video is really cute and light, and the song is really catchy. :D 

Does anyone know this? Thank you. :)