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softly; gently; quietly; lightly
stealthily; secretly; in secret
to leave alone; to leave as it is
眠っている赤ちゃんをそっと布団に寝かせた。
I gently laid the sleeping baby on the futon.
親に内緒でそっと家を抜け出して友達と会いに行った。
Without telling my parents, I stealthily slipped out of the house to meet a friend.
彼女はそっと肩に手を置いた。
She gently placed her hand on my shoulder.