I think it is a manhwa. Don't really remember the plot but after seeing a manhwa with similar drawing just have to find it. The plot described below might also not be completely correct.

Main character girl good at kendo. One day finds out the person she likes is her half brother (same father). Somehow gets pulled into another world (fell into water? The mother (her step mother) sent assassins?) In the other world she has to overthrow an evil queen. Later on finds out that she was originally part of the world and was somehow transported to the modern world when she was a baby. Three guy characters (that I remember may be more). One who she constantly sees in her dreams (a king?). Another who is an aristocrat (more of a cute type). Another with a dark background (slave? of the evil queen but later falls in love with her).

Sorry for the vague and uncertain descriptions but if anything comes to mind please reply. Thanks.

Saver?

YES! Thank you so much!

You're welcome!!