[Sentai]

Think about what we know.

We've seen Roshuo knows, and as experience with, Sagara. Sagara is capable of creating brand new Lockseeds. And from what we saw in this last episode Kouta was able to make a new one because he is becoming an Overlord. He used some sort of power to test Kouta before he could snatch the Fruit Basket LS from off the table. It's reasonable to assume that because he can travel back and forth between Helheim and our world so easily that he can create Cracks. Otherwise he'd be constantly waiting for one or sneaking through Yggdrasil's before it was destroyed. And The Mysterious Girl knows Sagara and exactly what he's capable of powerwise. Because she confronted him after Kachidoki Gaim destroyed Yggdrasil's superweapon.

With what we know, and what we can reasonably assume, is Sagara an Overlord?