Compress allows Atsuhiro to shrink anything in a spherical area into a small marble without actually damaging it.
To activate his Quirk, Atsuhiro needs to touch the target with his hand, which works even through his glove. The weight of the compressed objects is reduced considerably, making it possible to carry them around. Compress will also affect anything that is found within a specific range around the intended target, including, for example, fire or pieces of the ground.
If used on a person, Compress effectively entraps them, terminating the fight in an instant and letting Atsuhiro abduct them easily. This is particularly useful against opponents who are resistent to certain forms of attack, such as Snatch. If Atsuhiro focuses on an area smaller than the target's whole body, he is able to compress only said area, mutilating them.
Atsuhiro can release a single marble by wishing it, or all of them at the same time by snapping his fingers.
It appears this Quirk can be used in absolute stealth, without noise and before the victim can attract the attention of nearby allies.
This can come in handy to lay traps, which he demonstrated by throwing a marble under a police car and releasing his Quirk, causing the rock he had "compressed" to instantly recover its original size and launch the car upwards.
- Compression - Wikipedia article about the general effect caused by Atsuhiro's Quirk.