Gentle
A woman with cleats is walking on someone's back, but she doesn't want to hurt him. She has to be very gentle. Cleats are sharp and pointy, and not designed for back walking, so she's being extra, special gentle right now.
Picture a woman walking gently over someone's back. She's hardly moving.
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Actually, the person she's being gentle with is her dad (だ). No one would ever want to hurt their dad, especially if he's asked you to walk gently on his back as a way of giving him a massage.
Poor, old dad. His back hurts so his daughter has to walk on his back with cleats to make it feel better. But if she isn't gentle enough, she'll just make it worse.