Mephisto was making clones for the Demon Kings to inhabit. Father Fujimoto was one of them.

So was the man Satan possessed to father my brother and me.

[That's what he was able to figure out from the jump drive Lightning had given him. He needs to know more.]

Arc Knight Lewin Light passed the information on to me. [And he trusts that source. He trusts Lightning even if... even if there's one fewer person in Yukio's old family now.]