"...external story...independent of the person involved."
Sorry, I do not follow what you mean. Perhaps, then, I should try to explain what I mean. 
For me, love has no duty, in the usual way we think of duty: "conduct due to superiors; obligatory tasks."  Love always acts naturally for the ultimate well-being of others as is suited in the moment. Duty can overlook what is best for a perceived rightness of action. Duty comes from our understanding and effort.
However, in the Process of Spiritual Maturation, Duty is crucial in first half of life business and detrimental in second half of life freedom.