In a 'the proposal short story', if it's a business - related one, the main characters might be an entrepreneur and some potential investors. The entrepreneur would be presenting the proposal, trying to convince the investors to put their money into his or her idea. There could also be side characters like the entrepreneur's business partners or the investors' assistants.
If 'the proposal short story' is set in a historical context, the main characters could be a nobleman and a noblewoman. The nobleman might be proposing a marriage alliance for political or economic reasons. There could be other characters involved as well, such as their families who have different opinions on the proposal, and servants who help in the preparation of the grand proposal event.