TikTok has no feature to unfollow people in bulk, so you have to opt for third-party software. Some popular apps for the task are FuelTok, Socialpire, and Jarvee. However, those require a subscription (FuelTok and Jarvee have free trials).
If you want to complete the task for free and have access to a PC, you can use the TikTok Unfollower extension
