Boil water in a pot and add salt.

Cook spaghetti according to package instructions until al dente.

While spaghetti is cooking, prepare the mentaiko by removing the membrane and set aside.

Cut pea sprouts into manageable lengths and set aside.

Drain the cooked spaghetti and return it to the pot.

Add butter to the hot spaghetti and mix until melted.

Add mentaiko and pea sprouts to the spaghetti and mix gently.