"Like a knife cutting through water" is the Korean ideal of relationships within a family. The idea is that love among family members should be like water. You can cut through it with the sharpest of knives, but you can't keep it apart.
The first half is so good but the second half ruins the movie (the plot is easy to get and the acting is less impressive). About the series.... New Thitipoom's acting is...
https://www.laobayy.com/play/heisehuajizhengyan-1-1.html?fbclid=IwAR2Sn7Vrwr2C9zQRzV8tJWGBm_F_NFOuXhpuhy2giOsTQpJyINL1Lg7gxUE