Trim the okra and sprinkle with salt. Roll on a cutting board to remove fuzz.

Boil water in a pot, add salt and spaghetti, and cook according to package instructions. Add okra to the pot 1 minute before the spaghetti finishes cooking. Remove okra and cool in water. Drain the spaghetti.

Slice the okra thinly.

Cut open the mentaiko and extract the roe.

In a bowl, combine the spaghetti and butter, letting the residual heat melt the butter. Mix in mentaiko, okra, and mentsuyu.