Just passing by. No cubic is not a series. There are 2 parts: part 1 & part 2. Each part is fairly long, so they split it into 2 books each (just for easy handling). Part 2 is after they are together (don't remember if they got married or just gf/bf. The book seem to be very popular with many novel fans. The book fans doesn't seem happy with the cast because Mint is too pretty. Nang'k should be plain looking but a genius. In the beginning, Pra'k wants her pretty sister and overlook the plain looking Nang'k. Later, he fall in love with Nang'k for her ability, not her look.
The other series was called "Cupid". That one is a series of 8 novel. Currently, there is announcement to make lakorn out of them yet. Maybe the name similarity confuse a few people. Cubic is not the same as Cupid.