Dress Break practice!

"Oh? This that spell you were working on?" Rias asked Issei as he got up reluctantly.

"Yeah, pretty much. Actually, you can help out a bit," Issei told her, and she raised an eyebrow.

"Oh? You wanna practice on me too?" she purred, waggling her eyebrows. Issei chuckled and patted her shoulder.

"That definitely occurred to me, and you can definitely join in," Issei nodded. "But I also wish that Asia's room was stocked with outfits so I can practice the spell that destroys clothing as much as I need to."

"Done," she told him, snapping her fingers. They quickly headed to Asia's room, and they both stood side by side in front of Issei. "Let's get started~!" Rias chirped.

Issei nodded, then tapped both Asia and Rias, before taking a step back. "...Dress Break," he intoned, snapping his fingers. There was the sound of clothing tearing, but not much else. A few rips appeared in their clothes, but they remained intact, though Rias had one nipple showing. "...damn, was hoping for more," he groaned.

"Hey, this is your first time doing it on actual clothes, you only did peeling fruits and vegetables up to this point," Rias told Issei, not even bothering to adjust her top.

"Yeah, practice makes perfect, Master!" Asia chimed in. "...though I guess that's easy for me to say, given Akeno thinks I'm talented on top of having a Bishop piece..." she added sheepishly.

"Just try again until these clothes are completely destroyed," Rias instructed. "Then we'll put on a fresh set. We'll stop when you get to a point where you can consistently destroy them completely in one go."

"Got it," Issei nodded, before touching them again.

...

Three hours later, Issei was exhausted, and Asia and Rias were standing in front of him, fully clothed in fully intact clothes. "You're doing great," Asia told him, flushing slightly from all the times she had ended up naked.

"One more," Rias told Issei.

With the little magical energy he had left, he once again touched them, then snapped his fingers, activating Dress Break. The clothes immediately disintegrated, leaving Asia in nothing but the collar, and Rias in nothing period. "There we go! I got it!" Issei grinned, pumping a fist.

Rias giggled, before crossing her arms under her bust and leaning forward. "Yes, you did, Master... Now that you've unwrapped your prizes, how about claiming them?" she added teasingly.