If the opposite sex is a couple or husband and wife, or in the case of close relationship, walking alone can be regarded as an intimate behavior, because it is a relatively private and relaxing activity, which can promote emotional exchange and close relationship between the two sides. In addition, walking alone can also provide opportunities for both parties to be alone and further deepen their feelings.
But if the opposite sex is just an ordinary friend or acquaintance, walking alone may be just an ordinary social behavior, which may not necessarily have intimate significance. In this case, the two sides may just walk together because of the same interests or needs, which does not mean that they have a special emotional connection.
Therefore, whether the opposite sex walks alone is intimate or not depends on the specific situation, and needs to consider the relationship between the two sides, behavior performance and specific situation and background.