Lee Jae-in (Ha Seok-jin), a ruthless son from a wealthy family starts seeing an elementary school teacher, Kim Da-hyun (Jeon So-min) whom he has never seen before, on a six-month contract engagement, so that he could inherit the asset as written on his grandfather’s will. 'One Percent of Anything' is a romance drama depicting what happens to the pair during the fake engagement. 戴仁（何锦辰 饰）是圣贤集团会长李贵哲的孙子，年幼丧父的他从小在爷爷的严厉教导之下长大，个性迥异的爷孙两人在很多事上都存着分歧，随着时间推移，矛盾慢慢积累最终爆发，在和爷爷大吵一架后，戴仁离开了家，开始了独自一人的生活。 某日，戴仁意外得知爷爷立下遗嘱，上书如果戴仁不能迎娶名为多炫（全昭旻 饰）的女子，将会失去所有遗产的继承权。愤怒的戴仁将多炫当成了是欺骗和迷惑爷爷的骗子，两人之间产生了诸多的矛盾。然而，随着时间的推移，戴仁渐渐发现了多炫善良温柔的一面，一直扮演着纨绔子弟的戴仁，内心深处感受到了强烈的悸动。