That buckle is totally singing. Maybe this is why Haruto hasn't explained much about what exactly his powers involved? Or maybe it's the sort of thing that just needs to be demonstrated. He's grateful for her efforts at holding off the xenomutts, but he knows he needs to act faster.

"Transform!" His belt might have some Japanese left in it, but he doesn't. There's plenty of magic, though, activated when he passes his left hand with the blue and silver ring over that flashing buckle at his waist. "Water, please!" He then snaps the hand forward, projecting a glowing circle of magic runes before him. "Sui, sui, sui, suiiiii!" And he rushes through it, armor materializing around him as he comes out the other side.

And, now all transformed and ready to go, he is already moving into a spinning kick to punt the incoming xenomutt away.