Love Me Sinfully(2005)

Tsumi Bukaku Aishiteyo

Yuu Ono has been waiting impatiently to have the house all to himself while his parents fly to Guam for a weekend trip getaway. But no sooner do Mom and Dad board the plane than Yuu bumps into a mysterious man who whisks him away to an opulent hotel where he comes face-to-face with...himself?!

Pressed into becoming the body double for the Crown Prince of Qurd, Yuu's life is suddenly thrown into peril. Despite his misgivings about being the prince's double, Yuu can't help but trust the handsome bodyguard who swears, "I'll protect you, even at the cost of my life..." Hearing those words causes Yuu's heart to pound and sets his pulse racing! Maybe being a prince for a day won't be so bad after all.

(Source: DramaQueen)