As long as you search above, many online shopping platforms sell it. For example, one of the advertisements is like this: This product comes from South Korea and is the most stable automatic decoloring ink in the world at present. This kind of pen writes smoothly, and the writing color is the same as that of ordinary ink pen. After writing, the handwriting disappears naturally within a certain period of time, leaving no trace! Its time is 15 minutes to 7 days. If it encounters water, it will soon disappear, leaving only a blank sheet of paper! Illegal use is strictly prohibited! Can be used in the production process, such as making clothes markers, can also be used for students to draft, but also can be used for other purposes, with magical functions. Only used for clothing proofing, marking, etc. Jianghu is dangerous, sometimes things have to be done! Once you are forced to write down words or signatures against your will and be taken hostage, it may be a lifelong regret to be embarrassed to say anything! At this time, you can use self-disappearing ink, and it will disappear automatically after a while! The way out, you have to do it in danger, you have to do it! It cannot be used for illegal purposes, and it is strictly prohibited to use it illegally to write IOUs or contracts. Each bottle of 30ml medicine can be written in various forms, such as brush, pumping pen and pen, with blue and black ink.