Umbral translates to "threshold". It's a less common word in everyday Spanish, making it stand out in the lyrics.
In the song, it's used to describe being on the edge of a significant change or realization: "ser uno con el umbral / De esa delgada línea en la que el mundo te guiña / O te re caga a las piñas." This imagery of a threshold represents a critical point where life can either offer an opportunity or deliver a harsh blow, adding a layer of depth to the song's emotional landscape.
Milo J and Akriila build "Llora Llora" around a single instruction, repeated until it starts to feel like permission: cry. The hook doesn't hold back on the image either. "Llora, llora hasta que tus ojos sean mar" [Cry, cry until your eyes are the sea] turns tears into an ocean, and the next line keeps drawing it out: "Y tus pestañas la orilla donde abunda ese mal" [And your eyelashes the shore where that evil abounds].
The verses sound like someone talking to an older version of themselves, someone who's "casi treinta" [almost thirty] and still carrying "dos tajo' en las venas" [two cuts in your veins]. The line "Porque yo te vi morir casi ahogado por la sal de mar" [Because I saw you almost drown in the sea salt] takes the tears from the hook and turns them into something that nearly killed him. The song doesn't leave him there, though. "Pero yo sí que te quiero más que ayer" [But I love you more than yesterday] and "Voy a llevar las flores hasta que se marchiten" [I'm going to carry the flowers until they wither] are quiet promises to stay, even after everything.