https://tikcd.com/ What about this?
Download Tik Tok videos on mobile. If you want to save videos to your mobile phone, you need to launch the original application and find the video you want to download. When you are on the video watch page, you will see a "Share" button on the right of the screen. Click on it and then select "Save video" After that, the download will immediately begin. As soon as the download is complete, the video will be available on your phone.
and the you can transfer the original video into watermark-free version via this website TkTkDoWn - Free Download TikTok Videos in One-Click!
Via: Save tiktok video without watermark app