hex-sealed fusion rule

this monsters negates the fusion condition for the monsters they summon? i ever had this question and never get an answer u.u

no... the only thing is, that it special summons with its effect, it doesn't fusion summon

You can't use it it summon 'This card cannot be summoned except by fusion summon' monsters.

You can use it to summon 'This card cannot be fusion summoned except with the above fusion material monsters' monsters because it's not performing a fusion summon, just a special summon, so you can use it as a substitute.