[This video was shot with full consent of the model. The model was assured that she can pause or terminate the shooting and be released from any risky circumstances at any moment, by using predefined signals including but not limited to safe-words and safe-moves. WARNING: The video features performance by either professionals or under the supervision of professionals. Do not attempt to recreate any actions similar to the ones that appear in this video. No solo breathplay. NEVER.] Do you remember that Xiaoyu-senpai served as a prototype tester for Qianzhi K’s items in a previous video? Well, we’ve just received new prototypes, and this time Xiaomeng was eager to try them out first. We started with the first item. It was very similar to the valve mask—essentially a medical face mask combined with a threaded connector. This connector, instead of a valve, makes it easy to attach a hose or a rebreather bag. I connected it to a hose and a bubbler bottle, but oops! I had forgotten that a bubbler only works with one-way valves. When Xiaomeng exhaled, she ended up pushing a lot of water out through the inlet. At least this mishap confirmed the airtightness of the mask! We then moved on to testing it with a rebreathing bag, where the true capability of this new item became evident. Before long, Xiaomeng was breathless and completely exhausted. The second prototype was a latex face cover. It was a curved latex sheet designed to be secured over the face with six straps. Once properly fixed in place, it prevented Xiaomeng from inhaling any air, although she could still exhale. This caused her air reserve to deplete rapidly, leading to panic very quickly. In the end, we concluded that while the prototypes still need some tweaks, they are already highly effective in achieving their intended purpose! Thanks again to Qianzhi K (RIGHTSNEED) for the supply.