Touch Your Heart, Shopping King Louie, Marriage Not Dating, 100 Days My Prince, definitely not PURE fluff,. Like most K Dramas, they felt the need to add angst and darker elements, like the evil uncle in Shopping King Louie, the AWFUL mother in MND and the enforced separation in Touch Your Heart. The body count in 100 Days My Prince also rules it out as "pure" fluff.
"Pure fluff", without ANY darker elements is very hard to find, but Put Your Head on My Shoulder is a good example of how it can be done. Some that come close, but probably still fail to be 100% PURE fluff are Nigeru Wa Haji, Splash Splash Love, Le Coup de Foudre, A Love So Beautiful