The last chapter said "To be continued" tho, not "The End", so why it is 'completed'?

it could be an indicator of their repeated love story. like this is not the actual ending but just a beginning for them. bc it's completed in lezhin too.

Oh, so like we'll be getting new season?

i haven't heard anything about it, so i can't give a definite answer. but honestly i don't think so, bc the plot wouldn't allow creator to go further than this.