Rin can summon multiple familiars at once. He can also summon the same way Lewin does: abbreviated.

During the first Tamer test to see if they can summon, Rin just does his thing after Izumo summons her foxes and Shiemi summons Nee. He'd just been sitting in on the class and then gone "Howdy." And then summoned hellhounds.

Neuhaus walks out of the room to go get Lewin and it’s like “Oh, yeah, I taught him to do that.”

Everyone just gapes. That's when Ryuji's crush starts. He sees this Asian American boy with pretty blue eyes and cowboy boots and he summons Hellhounds with just a couple words, looking chiller than an iced coffee.

He was wearing a black dress shirt tucked into jeans and authentic cowboy boots. It shouldn't have looked good, but on that guy it did.

Rin never ceased to amaze Ryuji with his abilities.