Asesino literally translates to "killer" or "assassin." It's a strong, unexpected word to find in a romantic reggaeton song, which is exactly why it grabs the listener's attention so quickly.
Justin Quiles uses it metaphorically: "En esta escena seré tu asesino" ("In this scene I'll be your killer"), suggesting an intense, almost dangerous kind of passion rather than literal violence.
The hook is a scheduling problem. «Yo no quiero amarte» (I do not want to love you), Justin Quiles says, and then explains what he does want instead: «Quiero recogerte un viernes y entregarte un martes» (I want to pick you up on a Friday and drop you off on a Tuesday). Four days, returned by Tuesday. It is a blunt way to put it, and the whole song runs on how badly the rest of the lyrics contradict it.
Because he keeps describing something that sounds a lot like love. He wants «conocer más allá de tu timidez» (to know what is beyond your shyness), he has noticed «que tienes un lado oscuro» (that you have a dark side), and by the second verse Zion & Lennox are offering wine and a second date: «Dos copas de vino y un Franco de Vita» (two glasses of wine and some Franco de Vita), a Venezuelan balladeer whose songs are the opposite of casual. Then «Hoy tú y yo cambiaremos el destino» (today you and I will change our fate). That is not a four-day plan. The refrain never admits it.