Many members of the Pack take after their Vice-Captain, and use their own body as a weapon at least as often, if not more so, than their swords. So Koutarou kicking at Masaru doesn't really shock the swordsman.

That said, he's still impressed by the quick reflexes and flexibility involved in the maneuver. So it is indeed only a slash to the arm for Koutarou, and a kick to the side of the face for Masaru, who tilted his head to one side at the last moment.

The barrage of kicks has mixed success. The leg and shoulder strikes just graze Masaru, who is desperately trying to step and bend around the flurry of blows. The kick to his waist connects and begins spinning him around, which means that the kick to his head goes off course, and is stopped by the crossed forearms of Masaru.
Who probably could have used his swords there, but didn't want to maim a superior officer.
Still, even intercepted like that it's enough to drive him to his knees, and cause micro-fractures around him on the ground. Certainly a dramatic lesson in the power of a Shinigami's body if trained correctly.

But now what to do?

Masaru grunts and shoves his crossed arms up, driving Koutarou's leg away. Anticipating a kick from the other leg, he does a sloppy Shunpo a few feet away, finding his feet again and standing tall. He grins as he shakes his arms a bit to loosen them up. There's a fire in his eyes now, a desire to keep going. To test himself.

So that's why he waited, both swords now held in a traditional grip, the shorter one kept a bit closer to his body, while the longer is kept up in a guarding position.

Perhaps he actually wants to give Koutarou time to get out the whip again?