In "Honkai Impact: Star Rail", if you want to achieve the "Invisible Guest" achievement, you can follow the steps below:
1. Go to the east side of the 2nd floor of Flowing Dream Reef and buy a TV from NPC Gracie.
2. In the guest room compartment in the northern part of the Star Dome Train, place the TV at the light-emitting point.
3. Enter a room randomly after transforming into Hanu.
4. Finally, wait for the transformation to end to unlock the achievement "Invisible Guest".
The above is all about how to achieve the invisible guest achievement in "Honkai Impact: Star Rail". For more game strategies, please click the source code website.