Similar to Love Rain, Classic goes back and forth between the past and modern day, following different characters with various parallels. They are both heartfelt love stories, with nostalgia thrown in and lots of feels.
Both are romantic and bittersweet. The way some elements of the story come to light are similar.
Since Coffee Prince is a classic romantic comedy, here's another classic. There's no tomboy, but there are some pretty funny scenes and it's an easy watch.
If you want to continue down the road of dark melodrama and want to see more Lee Dong Wook than this may be the way to go. But be warned, A Bittersweet life in it's own way can be even darker than Hotel King with very little light hearted reprise. Like Hotel King, it also has a very good Romance, although the romantic couple have a completely different vibe.