Seiya knew that Furuta as a problem was meant to be solved by his own hand and if he didn't handle it then the other two would get harmed as a result of his own incompetence.
He couldn't let this man hurt them.
Not when he's already dealt with the likes of Shoichi's father who he could tell was stronger than Furuta.
This didn't mean Furuta was any less deadly with that poison ability that is connected to his blade.
Seiya didn't want to get caught by that mist, not after the first incident but in a way he had been in a safer position since Furuta didn't follow it up with his natural mist.
Their battle was only halted by the two of theirs staredown, they were trying to gauge what the other was doing but with no discernible movements this lasted for a time.
