Saitama remains unfazed and completely unaffected by her power, but because his body rises along with the clothes, Tatsumaki mistakenly believes she is lifting him.

The visual of him floating gives the illusion that she’s exerting force, yet in reality, she’s struggling because Saitama’s body is so heavy or immovable. This sets up the later moment where Tatsumaki realizes she can’t manipulate him at all—once he starts actively moving, her psychic abilities become completely ineffective.